Distant Recurrence-free Survival Research Articles

Integrating Imaging and Circulating Tumor DNA Features for Predicting Patient Outcomes

Biomarkers for evaluating tumor response to therapy and estimating the risk of disease relapse represent tremendous areas of clinical need. To evaluate treatment efficacy, tumor response is routinely assessed using different imaging modalities like positron emission tomography/computed tomography or magnetic resonance imaging. More recently, the development of circulating tumor DNA detection assays has provided a minimally invasive approach to evaluate tumor response and prognosis through a blood test (liquid biopsy). Integrating imaging- and circulating tumor DNA-based biomarkers may lead to improvements in the prediction of patient outcomes. For this mini-review, we searched the scientific literature to find original articles that combined quantitative imaging and circulating tumor DNA biomarkers to build prediction models. Seven studies reported building prognostic models to predict distant recurrence-free, progression-free, or overall survival. Three discussed building models to predict treatment response using tumor volume, pathologic complete response, or objective response as endpoints. The limited number of articles and the modest cohort sizes reported in these studies attest to the infancy of this field of study. Nonetheless, these studies demonstrate the feasibility of developing multivariable response-predictive and prognostic models using regression and machine learning approaches. Larger studies are warranted to facilitate the building of highly accurate response-predictive and prognostic models that are generalizable to other datasets and clinical settings.

Abstract PO4-02-12: MDA iLobular Prognostic Tool: A Novel Approach for Risk Stratification in Invasive Lobular Carcinoma

Abstract Background: Invasive lobular carcinoma (ILC) is a distinct subtype of breast cancer that differs from the more common invasive ductal carcinoma (IDC) by its unique characteristics that influence prognosis. Recent studies have shown that ILC is associated with worse long-term outcomes compared to IDC. Risk stratification is essential in breast cancer for tailoring treatment plans to the individual patient’s needs, maximizing the chances of successful outcomes and minimizing unnecessary interventions. Although there are multiple tools available for breast cancer, there is currently not a risk stratification tool that is specific for ILC. The MDA iLobular prognostic tool is the first risk stratification tool that has been developed specifically for ILC patients. Methods: We retrospectively searched for patients treated at MD Anderson Cancer Center with a diagnosis of stage I-III ILC in our prospectively collected electronic database. The study focused on two primary endpoints: Overall Survival (OS) and Distant Recurrence Free Survival (DRFS). We utilized univariate and multivariate Cox Proportional Hazard (PH) regression models to assess the statistical significance of all variables. The univariate Cox analysis identified prognostic factors, which were further analyzed using backward and stepwise multivariate Cox proportional hazards regression analysis. This process helped identify statistically significant prognostic factors that were included in the final multivariate models. We estimated hazard ratios and 95% confidence intervals for each factor, considering a P-value of < 0.05 as statistically significant. To evaluate the performance of the fitted multivariate Cox PH regression models for OS and DRFS, we randomly divided two-thirds of the data points into a training dataset, while the remaining one-third constituted the test dataset. We assessed the discrimination capacity of each model using Harrell's C-index. Results: The study included a total of 4,216 female patients, with a median age of 56 years. The median pathological tumor size was 2 mm, and the median number of lymph nodes was one. Among these patients, 1,376 were pre-menopausal, while 2,837 were post-menopausal. The training cohort was a subset of 2,950 patients and the test cohort was a subset of 1,266 patients. After evaluating various prognostic models, we identified the model with the highest prognostic accuracy for OS and DRFS. This selected model demonstrated a Harrell's C-index of 0.704 for OS and 0.718 for DRFS on the training dataset and a Harrell's C-index of 0.702 for OS and 0.671 for DRFS on the test dataset. The model incorporated several covariates, including age at the time of diagnosis, number of lymph nodes, pathological tumor size (mm), ER status, tumor grade, ILC histology, and the presence or absence of concomitant LCIS (Table 1). Conclusion: In conclusion, the MDA iLobular prognostic tool represents a significant advancement as the first dedicated tool for risk stratifying ILC, providing valuable guidance for tailoring therapy to individual ILC patients based on their specific risk profiles. Table 1. Multivariate Cox proportional hazard model parameter estimates for OS and DRFS Citation Format: Jason Mouabbi, Sarah Pasyar, Roland Bassett, Akshara Singareeka Raghavendra, Amy Hassan, Rachel Layman, Debu Tripathy. MDA iLobular Prognostic Tool: A Novel Approach for Risk Stratification in Invasive Lobular Carcinoma [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-02-12.

Abstract PO5-01-08: The impact of Human Epidermal growth factor Receptor 2 (HER2) expression by RT-PCR on tumor characteristics and outcome in estrogen receptor (ER) positive, HER2 negative early-stage breast cancer

Abstract Background: The role of HER2 expression in HER2 negative breast cancer is evolving. Whether HER2 expression has an impact on ER positive, HER2 negative early-stage breast cancer in unclear. Oncotype DX assay Recurrence Score comprises of standardized quantitative HER2 mRNA expression levels by RT-PCR. The objective of this study was to investigate the impact of Oncotype HER2 score on tumor characteristics and outcome. Methods: All women assigned to the Clalit Health Services registry between 2006 to 2011 with ER positive, HER2 negative early-stage breast cancer whose tumor were sent for oncotype were identified. Patients in which HER2 score was reported in the oncotype results were included. Differences in age, tumor characteristics and chemotherapy administration between lower HER2 score (H1), i.e. HER2 score ≤ 9.1, to higher HER2 score (H2), i.e. 9.2-10.7, were analyzed. 5-year Kaplan–Meier for distant recurrence free survival (DRFS) and overall survival (OS) were estimated and differences between H1 and H2 were evaluated. Analyses were repeated separately for node negative and for node positive (N mic and 1-3 lymph nodes) disease. Results: A total of 1535 patients were included, 948 patients with node negative disease and 587 with node positive disease. Of these, 814 and 721 patients were categorized to the H1 and H2 groups, respectively. Median follow-up was 5.4 years. The distribution of oncotype RS was different, with significantly lower proportion of patients with RS between 0-10 and higher proportion of RS above 25 in the H1 group compared to the H2 groups. This difference was identified both for patients with node negative and node positive disease (Table). The distributions of age, tumor size and histological subtype were comparable between the H1 and the H2 groups, both for node negative and node positive disease. Within each RS group, administration of chemotherapy was comparable between H1 and H2 groups, regardless of nodal involvement. DRFS and OS were not associated with HER2 score. For RS 0-25, node negative disease, 5-year DRFS was 96.2% in H1 and 96.4% in H2 groups (p=0.92) and 5-year OS was 97.2% in H1 and 98.1% in H2 groups (p=0.39). For RS >25, node negative disease, 5-years DRFS was 89% in H1 and 90.8% in H2 groups (p=0.33) and 5-year OS was 90.6% in H1 and 90.8% in H2 groups (p=0.7). Similarly, for node positive disease, DRFS and OS were comparable between H1 and H2 group in all subgroups. Conclusions: Low HER2 mRNA expression by Oncotype RT-PCR assay was associated with significantly high Oncotype RS. Patients' outcome was not directly affected by HER2 score and was determined by RS. Further study is desired to clarify the role of HER2 expression in early stage, luminal breast cancer. Table. Comparison of age and tumor characteristics between low (H1) and high (H2) HER2 score Citation Format: Hadar Goldvaser, Raz Mutai, Salomon Stemmer, Iryna Kuchuk, Margarita Tokar, Shani Paluch-Shimon, Rinat Yerushalmi, Karen Drumea, Ella Evron, Amir Sonnenblick, Einav Gal-Yam, Gil Bar Sela, Ayelet Shai, Rotem Merose, Avital Bareket-Samish, Lior Soussan-Gutman. The impact of Human Epidermal growth factor Receptor 2 (HER2) expression by RT-PCR on tumor characteristics and outcome in estrogen receptor (ER) positive, HER2 negative early-stage breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-01-08.

Abstract PO1-14-11: Different molecular processes are associated with recurrence in the clinical high- genomic low risk (cH/gL) and clinical low- genomic high risk (cL/gH) groups of the MINDACT clinical trial

Abstract Background: Despite the growing understanding of estrogen receptor positive/HER2-negative (ER+/HER2-) breast cancer (BC) biology, many unknowns remain regarding the mechanisms of disease recurrence. While several multigene prognostic signatures have shown clinical utility in identifying those patients at high or low genomic risk of recurrence, they can present with some limitations. In this retrospective analysis of the MINDACT trial, we interrogated the available transcriptomic data to understand which biological characteristics of the tumor are associated with recurrence in patients from the clinical high- genomic low risk (cH/gL) and clinical low- genomic high risk (cL/gH) groups (where the clinical and genomic risk were defined by a modified version of Adjuvant Online! and the 70-gene signature, respectively). Methods: These analyses focused on the subset of patients with ER+/HER2- tumors of no special type (NST) who received endocrine therapy (which comprised the majority of this NST ER+/HER2- sub-cohort) and for which central pathology and gene expression data were available (n= 1245). Scores of gene expression modules associated with key biological processes in breast cancer defined in a collection of previous publications were computed from the gene expression matrix using the formula described in Desmedt et al. (Clin. Cancer Res. 2008). Gene Set Variation Analysis method (R package ‘GSVA’ – version 1.40.1) was used to derive the enrichment scores of fifty hallmark gene sets available in the ‘H’ collection of the MSigDB database (version 7.5.1). Survival analyses were performed for disease-free survival (DFS) and distant recurrence-free survival (DRFS). Univariable and multivariable regression models, implemented by Cox regression and Fine-Gray subdistribution hazard regression methods, were performed to evaluate the association of enrichment of hallmarks and gene modules with DFS and DRFS, respectively (covariates =age, nodal status, KI67, tumor size, chemotherapy, radiotherapy). Results: DFS event occurred in 150/913 (16.4%) and 51/332 (15.4%) NST ER+/HER2- patients in the cH/gL and cL/gH groups, respectively. DRFS event occurred in 70/913 (7.7%) and 21/332 (6.3%) NST ER+/HER2- patients in the cH/gL and cL/gH groups, respectively. In the cH/gL group, we observed an association of hallmarks related to cell cycle and downregulation of gene modules related to lymphocyte-centric immune activities with worse prognosis (Table). For the cL/gH, we did not observe an association between hallmarks related to cell cycle and worse prognosis but an enrichment of hallmarks related to PI3K/AKT/mTOR signaling as well as several metabolic hallmarks related to insulin activities (Table). Of interest, in this group of patients, higher scores of the HER2-associated gene expression signature were also associated with worse prognosis. Across the two groups effects were more pronounced for DRFS than DFS. Conclusion: Different molecular processes are associated with progression in these two distinct groups of patients. The association of hallmarks related to cell cycle with survival in the cH/gL group supports the observation that adjuvant chemotherapy could benefit a subset of these patients. In the cL/gH group, the association of signatures associated with PI3K pathway and HER2 can have potential clinical relevance given their current targetability in the metastatic setting. This retrospective study is funded by the Breast Cancer Research Foundation. Table. Representative hallmarks and gene expression modules independently associated with prognosis in NST ER+/HER2- patients in the cH/gL group and in the cL/gH group #p-values reported were not corrected for multiple testing Citation Format: Christine Desmedt, Ha-Linh Nguyen, François Richard, Marion Maetens, Coralie Poncet, Laura De Meulemeester, Kim Aalders, Mauro Delorenzi, Suzette Delaloge, Jean-Yves Pierga, Etienne Brain, Suzan Vrijaldenhoven, Peter A Neijenhuis, Emiel Rutgers, Florentine Hilbers, Laura Van ’t Veer, Giuseppe Viale, Christos Sotiriou, Martine Piccart, Fatima Cardoso. Different molecular processes are associated with recurrence in the clinical high- genomic low risk (cH/gL) and clinical low- genomic high risk (cL/gH) groups of the MINDACT clinical trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-14-11.

Abstract PO1-01-13: Clinical characterization, prognostic and predictive values of HER2-low in early breast cancer in the PALLAS trial

Abstract Background: Low levels of HER2 expression (HER2-low) have recently emerged as a therapeutic target in patients (pts) with breast cancer (BC). The aim of this study was to evaluate clinical and demographic variables associated with HER2 expression, as well as the value of HER2-low as a prognostic and predictive biomarker for palbociclib benefit in pts enrolled in the PALLAS trial. Methods: The phase III PALLAS trial investigated the addition of palbociclib to adjuvant endocrine therapy (ET) in pts with stage II-III hormone receptor-positive BC. The aims of this analysis are (1) to assess the association between the presence of low levels of HER2 expression with demographic and clinicopathological parameters, (2) to test the prognostic value of HER2-low status on invasive disease-free survival (IDFS), distant relapse-free survival (DRFS), and overall survival (OS) and (3) to assess the value of HER2 expression as a predictive biomarker of response to palbociclib. HER2-low was defined as HER2 immunohistochemistry (IHC) 1+ or IHC 2+ with negative in situ hybridization; all pathologic evaluation was performed locally. Pts with HER2-0 and Her2-low BC were included in this analysis; those with HER2-positive BC or missing HER2 status were excluded. Association of HER2 with other baseline covariates were tested with Chi-squared tests. Prognostic and predictive power of HER2 were assessed with Cox Models. Multivariable models included age, T-stage, N-stage, grade and progesterone receptor (PR) expression. Hazard ratios (HR) and 95% Confidence intervals (CI) are reported. Results: From the original PALLAS intention-to-treat population (N = 5,753), 5304 pts (92.2%) were included in this analysis. Among these, 2,254 pts (42.5%) were classified as HER2 IHC 0 (HER2-0) and 3,050 (57.5%) as HER2-low (1,838 with IHC 1+ and 1,212 with IHC 2+). For this analysis, median follow-up was 59.8 months. Compared to HER2-0, pts with HER2-low tumors had statistically higher estrogen receptor expression levels (mean expression 89.2% vs 88.2%, p = 0.019), lower PR expression levels (65.9% vs 68.2%, p = 0.007). Importantly, HER2-low status varied significantly across 21 participating countries (range 16.7% to 75.6%; p< 0.001) and was more frequent in pts enrolled in North America (63.1%) than in Europe (53.4%) and other regions (53.4%) (p < 0.001). No differences in HER2 expression were observed according to anatomic stage, T-stage, N-stage, histological grade, age, menopausal status, primary surgery type, prior radiation, prior chemotherapy, or baseline performance status. There were no statistically significant differences in IDFS, DRFS or OS according to HER2 status in univariate or multivariable Cox models (prognostic value, HR provided in the Table). There was no significant interaction between the HER2 status and the benefit to palbociclib in IDFS, DRFS or OS (Table). Similar results were obtained when HER2-0 was compared to HER2 1+ and HER2 2+ separately. Conclusions: In this large, prospective and international cohort, no differences were observed in clinical parameters, prognosis, or differential benefit from palbociclib (predictive value) between HER2-0 and HER2-low tumors. Significant geographic variability was observed in the prevalence of HER2-low status, suggesting a high degree of variation in pathologic assessment of HER2 expression without impact on outcomes. Support: AFT, Abbvie Pfizer; Clinicaltrials.gov: NCT02513394 https://acknowledgments.alliancefound.org Citation Format: Guilherme Nader-Marta, Christian F. Singer, Dominik Hlauschek, Angela DeMichele, Paolo Tarantino, Georg Pfeiler, Miguel Martín, Justin Balko, Zbigniew Nowecki, Marija Balic, Adam Brufsky, Arlene Chan, Patrick G. Morris, Tufia Haddad, Sibylle Loibl, Yuan Liu, Lidija Sölkner, Christian Fesl, Erica Mayer, Michael Gnant. Clinical characterization, prognostic and predictive values of HER2-low in early breast cancer in the PALLAS trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-01-13.

Abstract GS03-06: Genomic and transcriptomic profiling of primary tumors from patients with HR+, HER2-, node-positive, high-risk early breast cancer in the monarchE trial

Abstract Background Two years of adjuvant abemaciclib combined with endocrine therapy (ET) resulted in significant and clinically meaningful improvement in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) in patients (pts) with HR+, HER2-, node-positive, high-risk early breast cancer in the monarchE trial (NCT03155997). Abemaciclib benefit was sustained beyond the completion of treatment (tx) with deepening magnitude of absolute benefit in IDFS and DRFS at 5 years. Here, we evaluate comprehensive molecular profiling of archived primary tumor tissue and association with clinical outcomes. Methods For biomarker analysis, a proportionally stratified random sampling case-cohort design was utilized to include all patients who experienced an IDFS event at a pre-specified interim analysis with a median follow up of 54 months. A cohort of 895 pts (189 with IDFS event) in the abemaciclib + ET arm was matched 1:1 with 903 pts (270 with IDFS event) in the ET arm. Baseline primary tumor samples underwent exome-capture RNA sequencing (RNAseq; n=1324, 23% intent-to-treat (ITT) population) and paired tumor-normal (germline blood samples) whole-exome sequencing (WES; n=1234, 22% ITT population). Expression-based intrinsic subtypes (i.e., luminal A (LumA), luminal B (LumB), HER2-enriched (HER2E), basal- and normal-like) were characterized using the Absolute Intrinsic Molecular Subtyping model. The 21-gene expression signature score (Oncotype DX test) was inferred from RNAseq; samples were categorized into lower (0-25) and high (26-100) risk groups. To investigate associations of biomarkers with abemaciclib benefit, WES genomic events including oncogenic and hotspot mutations by OncoKB, and copy number events, of incidence >9% were pre-selected. Results The biomarker subset of monarchE was reflective of the ITT population. A total of 1190 tumors (abemaciclib+ET n= 605; ET alone n=585) yielded adequate RNAseq results. Intrinsic subtype distribution was consistent across tx arms (Table A). Low tumor purity limited assessment of the normal-like subtype. The 4-year IDFS benefit of abemaciclib was consistent across all subtypes. LumA cancers had the lowest risk of recurrence while HER2E and basal-like subtypes had the highest. Inferred 21-gene expression signature score showed similar benefits from abemaciclib in both lower and high-risk groups (Table B). A total of 1173 tumors yielded adequate WES results (abemaciclib+ET n=580; ET alone n=593). Consistent abemaciclib benefit was observed across the most frequently altered genes (Table C). In exploratory analysis, lower benefit from abemaciclib was seen in the subset of focal-high level MYC amplified tumors (n=176, HR 1.30, 95% CI, 0.77, 2.20) compared to MYC non-amplified tumors (n=997, HR 0.62, 95% CI, 0.47, 0.80, nominal interaction p=0.014). The treatment benefit of abemaciclib was observed across all subpopulations of altered genes based on gene expression data. Conclusions Adjuvant abemaciclib+ET maintained IDFS benefit compared to ET alone across all molecular subtypes as measured by RNAseq. Benefit was consistent across most altered genes assessed by WES, except for the subset of tumors with MYC amplification. Additional research is necessary to confirm these findings. Table. Citation Format: Nicholas Turner, Jorge Reis-Filho, Matthew Goetz, Christine Desmedt, Sarat Chandarlapaty, Hironobu Sasano, Carlos Arteaga, Sherene Loi, Stephanie Graff, Deli Liu, Vanessa Rodrik-Outmezguine, Anthony Sireci, Cynthia Sandoval Rubenstein, Helen Won, Lacey M. Litchfield, Maria Munoz, Stephen Johnston. Genomic and transcriptomic profiling of primary tumors from patients with HR+, HER2-, node-positive, high-risk early breast cancer in the monarchE trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr GS03-06.

Abstract PS06-01: Results from a pilot study exploring ctDNA detection using a tumor-informed assay in the monarchE trial of adjuvant abemaciclib with endocrine therapy in HR+, HER2-, node-positive, high-risk early breast cancer

Abstract Background Two years of adjuvant abemaciclib + endocrine therapy (ET) resulted in significant and clinically meaningful improvement in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) in patients (pts) with HR+, HER2-, node-positive, high-risk early breast cancer (EBC) in the monarchE trial (NCT03155997). The benefit of abemaciclib was sustained beyond completion of treatment and deepened in magnitude at 4 years for IDFS and DRFS. This pilot study investigated the technical feasibility of ctDNA detection beginning prior to study treatment, as well as rates of persistence and clearance in a subset of EBC pts from monarchE using the clinically validated SignateraTM ctDNA assay. Methods Samples were analyzed from a selected subset of pts (n=178; 84 from abemaciclib+ET arm; 94 ET alone) who had blood collected both before initiating protocol directed therapy, Visit 1 (V1; randomization + ≤ 3 days) and near completion of the 2-year treatment period, Visit 27 (V27; 24 months +/- 5 days from V1). This cohort of pts was enriched for overall IDFS events compared to the total monarchE study population, however pts with relapses occurring prior to V27 were excluded. Primary tumors from selected pts were subjected to whole exome sequencing (WES). Selected samples included those from pts with a range of tumor mutation burden. Cell-free DNA was extracted from 356 plasma samples. A Signatera ctDNA assay was developed for each pt based on up to 16 variants detected by WES from each baseline tumor sample. Results The IDFS event rate for the selected subset (n=178) was 39.3% (abemaciclib+ET 34.5% [29/84] and ET alone 43.6% [41/94]). Ten pts (5.6%) were initially ctDNA+ and 42 pts (23.6%) were persistently (7 pts, 3.9%) or became (35 pts, 19.7%) ctDNA+ at V27. Notably, 70% of pts who were initially ctDNA+ and 100% of pts who were either persistently ctDNA+ or became ctDNA+ experienced recurrence (see Table 1). In contrast, none of the 3 pts that cleared ctDNA+ developed recurrence. In pts persistently ctDNA negative (neg), 28 (21.1%) experienced recurrence. Overall, 10% (7/70) of pts with IDFS events were initially ctDNA+ and 50% (35/70) had detectable ctDNA at V27. Conclusions Detection of ctDNA soon after completing neoadjuvant chemotherapy was infrequent, but also associated with a high-risk of recurrence. ctDNA positivity was common at the end of the 2-year treatment period and was highly prognostic with all pts subsequently developing disease recurrence. Importantly, ~30% of pts with early ctDNA detection ultimately dropped below detection limits during the 2-year treatment period and none developed recurrence. Although some pts remained persistently ctDNA neg during this study and experienced recurrence, the delay in recurrence may indicate longitudinal benefit from remaining ctDNA neg. Future planned analysis of an expanded cohort reflective of the intent to treat population including additional timepoints within the 2-year treatment period will further define how ctDNA dynamics may identify pts at high-risk of recurrence. Table 1. Summary of Subset Positivity Rates. + positive; - negative; NA, not applicable. Citation Format: Sherene Loi, Stephen Johnston, Carlos Arteaga, Stephanie Graff, Sarat Chandarlapaty, Matthew Goetz, Christine Desmedt, Jorge Reis-Filho, Hironobu Sasano, Vanessa Rodrik-Outmezguine, Anthony Sireci, Cynthia Sandoval Rubenstein, Helen Won, Deli Liu, Lacey M. Litchfield, Nicholas Turner. Results from a pilot study exploring ctDNA detection using a tumor-informed assay in the monarchE trial of adjuvant abemaciclib with endocrine therapy in HR+, HER2-, node-positive, high-risk early breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS06-01.

Abstract PO1-01-08: The impact of drug-drug interactions between palbociclib and proton pump inhibitors on clinical outcomes of patients with hormone receptor positive, HER2-negative, early breast cancer: an exploratory analysis of the PALLAS study

Abstract Background: Data suggest that concomitant intake of proton pump inhibitors (PPI) may create drug-drug interactions, potentially impacting efficacy of agents including palbociclib, which is widely used in the treatment of metastatic hormone-receptor-positive/HER2-negative (HR+/HER2-) breast cancer. In the open label, randomized, phase 3 PALLAS trial, the addition of palbociclib for two years to standard adjuvant endocrine therapy (ET) in patients with HR+/HER2- early breast cancer (EBC) did not improve invasive disease-free survival (IDFS) compared to adjuvant ET alone. We explored whether concomitant use of PPIs could have affected clinical outcomes in patients treated with palbociclib in PALLAS. Methods: This is an exploratory, unplanned analysis of the PALLAS trial (AFT-05/ABCSG-42/PrE0109/BIG-14-13, NCT02513394), which enrolled 5796 patients with stage II-III HR+/HER2- EBC. Patients were randomized to receive either 2 years of palbociclib (125 mg oral capsules once daily on days 1-21 of a 28-day cycle) with adjuvant ET or ET alone. Primary endpoint was IDFS in the intention-to-treat population. The present exploratory analysis included patients who received at least one dose of palbociclib. Definitions of IDFS, distant relapse-free survival (DRFS) and overall survival (OS) were according to the PALLAS protocol (STEEP criteria), using first day of palbociclib intake as start date. Only PPI concomitant intake during palbociclib treatment was considered. To determine the association of concomitant PPI use with IDFS, DRFS, and OS, uni- and multivariable Cox models with time-dependent PPI (the latter adjusted for age, prior chemotherapy, progesterone receptor, grade, tumor stage, nodal stage, body mass index (BMI)) were used. Also, the association between PPI use and neutropenia was investigated in patients initiating PPI prior to randomization vs never. Odds ratios (OR) unadjusted and adjusted for age and BMI estimated with logistic regression models are reported. Results: Of 2840 patients treated with palbociclib + ET, 533 (18.8%) had concomitant PPI and palbociclib intake. Median duration of PPI intake was 10.8 months (interquartile range 2.3-22.3). Most patients received omeprazole as PPI (n=265, 49.7%). PPI intake was significantly associated with older age, post-menopausal status, use of aromatase inhibitors as ET, higher BMI, and worse ECOG status (all p< 0.001). Concomitant PPI intake was not significantly associated with survival outcomes (Table 1). Unadjusted all grade neutropenia rates were slightly lower in patients who initiated PPI prior study start vs patients never initiating (79% vs 85%, unadjusted OR 0.66, 95%CI 0.50-0.88). After adjustment for BMI and age, the difference between the groups decreased (adjusted OR = 0.77, 95%CI 0.57-1.04). Similar effect sizes were found for grade 3/4 neutropenia rates (54% vs 64%, unadjusted OR 0.66, 95%CI 0.52-0.83, adjusted OR 0.81, 95%CI 0.64-1.03). Conclusions: Our exploratory analysis did not demonstrate a statistically significant relationship between concomitant use of PPIs and palbociclib and survival outcomes of patients in the PALLAS trial. Nonetheless, careful consideration of concomitant medications and of drug-drug interactions is important when studying novel agents in the adjuvant breast cancer setting. Support: AFT, Pfizer; https://acknowledgments.alliancefound.org Table 1. Association between PPI intake and survival outcomes. Citation Format: Elisa Agostinetto, Georg Pfeiler, Dominik Hlauschek, Erica Mayer, Matteo Lambertini, Evandro de Azambuja, Meritxell Bellet- Ezquerra, Jane Meisel, Gabor Rubovszky, Nicholas Zdenkowski, Yelena Novik, Manuel Ruíz - Borrego, Karen Gelmon, Eleftherios Mamounas, Hiroji Iwata, Dongrui Lu, Lidija Sölkner, Christian Fesl, Michael Gnant, Angela DeMichele. The impact of drug-drug interactions between palbociclib and proton pump inhibitors on clinical outcomes of patients with hormone receptor positive, HER2-negative, early breast cancer: an exploratory analysis of the PALLAS study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-01-08.

Abstract PO4-20-05: An open label phase III randomized trial to evaluate the efficacy of Post-chemotherapy Axillary Conservation Surgery in breast cancer (PACS)

Abstract Background- Axillary lymph nodes (ALN) status is the most important prognostic factor in breast cancer. Traditionally, a complete axillary lymph node dissection (ALND) has been standard of care for those patients who have a positive node pre-chemotherapy. However, lately axillary conservation is paving its way in the post-chemotherapy setting as well to avoid significant morbidity of ALND. Most sentinel node biopsy studies have failed to achieve the desired false negative rate(FNR). (Boughey JC et al, JAMA. 2013 Oct; Kuehn T et al, Lancet Oncol. 2013; Boileau JF et al, J Clin Oncol. 2015 Jan).We previously reported a low FNR of low axillary sampling (LAS) in the post-chemotherapy setting. (Parmar et al, JCO-GO, 2021) We are conducting a phase III, randomised controlled trial of LAS versus complete ALND in post-chemotherapy negative (ypN0) axilla. Aims and objectives- The primary objective is to assess the non-inferiority of LAS in patients who are rendered ypN0 by pre-operative chemotherapy with disease-free survival as primary end point. The secondary objectives are comparing the morbidity of ALND (lymphedema, paraesthesia, and shoulder dysfunction) in the LAS and ALND arms, and to evaluate the impact on overall survival, local, regional, and distant recurrence free survival and quality of life. Trial design- This is a prospective, open label, randomised, phase III trial where histologically proven, non-metastatic, cT1-4,N0-2 breast cancer patients who are rendered ycN0 after pre-operative systemic chemotherapy are being accrued. Patients with prechemo N3 disease, inflammatory breast cancer, recurrent disease, pregnancy associated breast cancer are being excluded from the study. The chemotherapy regimens and surgical assessment is as per standard institutional protocols. After obtaining informed consent, patients undergo LAS during surgery and lymph nodes(LN) are sent for frozen section analysis. If any LN is found to be involved, a complete ALND is carried out. If the staging procedure is negative, then patients are randomised into 2 groups- observation v/s complete ALND. Stratification factors are T stage, N stage, Hormone receptor status, Her2 receptor status and number of chemotherapy cycles taken. Morbidity assessment is done with- Constans shoulder score, arm volumetry, paraesthesia assessment, and a QOL questionnaire- Self-reported Breast cancer Lymphedema Symptom Experience Index (BCLSEI). A baseline assessment pre-surgery is followed by 6 monthly morbidity assessments and regular oncologically relevant follow-up up to 5 years. A two-sided log-rank test with an overall sample size of 2316 with a 10% dropout rate (1158 in ALND and 1158 in LAS group) achieves 80% power at a 0.05 significance level to detect a hazard ratio of 1.16 (upper limit of non-inferiority) when the proportion surviving in the control group is 0.71. An interim analysis will be carried out at 25% events and conditional power will be calculated. If the conditional power is below 20%, then the study will be discontinued for futility. The study has been approved by Institutional Ethics Committee (CTRI/2022/07/044461) Expected Study and Results- We started accrual in February 2023 and have screened 63 and randomized 45 patients until now. Ours is a first large randomised prospective study in the post-chemotherapy axillary management setting which will help us understand the efficacy of axillary conservation surgery in patients who are node negative post neoadjuvant chemotherapy. In future, lesser morbid procedures than LAS like targeted axillary dissection can be tested in the same trial. However, LAS as a technique of axillary conservation suits resource constraints and high volume setting such as ours. Citation Format: Shalaka Joshi, Jessicka Shah, Pallavi Daphale, Rohini Hawaldar, Anuradha Daptardar, Ayushi Sahay, Tanuja Shet, Palak Popat, Tabassum Wadasadawala, Nita Nair, Vani Parmar, Bipin Bandre, Shabina Siddique, Vaibhav Vanmali, Sudeep Gupta, Rajendra Badwe. An open label phase III randomized trial to evaluate the efficacy of Post-chemotherapy Axillary Conservation Surgery in breast cancer (PACS) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-20-05.

Abstract PO2-22-05: A prospective phase I-II study of hypofractionated accelerated breast and nodal intensity modulated radiation therapy delivered in the prone position

Abstract Background In patients with breast cancer, prone radiotherapy (RT) has been shown to reduce heart and lung dose. Routinely used for whole breast (WB) RT, its use to treat regional lymph nodes (LNs) is not widespread. Methods In this phase I-II study (NCT02308488) patients treated with lumpectomy or mastectomy with 1-5 pathologically involved LNs underwent WBRT or post-mastectomy RT plus regional nodal RT using IMRT to the supraclavicular and level III axillary LNs. The prescription was 40.5Gy in 15 daily 2.7Gy fractions with a daily concomitant 0.5Gy tumor bed boost. Patients who underwent sentinel LN biopsy (SLNB) alone (no axillary dissection) had the level I-II axilla included in the RT field. The primary endpoints were incidence of >grade 2 acute toxicity per CTCAE v 3.0 and dosimetric feasibility. The secondary endpoint was late toxicity. Clinical outcomes were local recurrence (LR), disease free survival (DFS), distant recurrence free survival (DRFS) and overall survival (OS). Coverage constraints included planning target volume [PTV] V48Gy ≥ 98%, PTV breast V40.5Gy ≥ 95% and PTV nodes V38.5Gy ≥ 95%. Normal tissue constraints included heart V5Gy < 5%, ipsilateral lung V10Gy < 20%, contralateral lung V5Gy < 15%, ipsilateral brachial plexus (BP) maximal dose (Dmax) < 42Gy, spinal cord Dmax ≤ 3 7.5Gy, thyroid contralateral lobe Dmax ≤ 15Gy, esophagus V30Gy < 50% and Dmax ≤ 40.5Gy. Results From 2011-2016, 97 patients with stage IB-IIA breast cancer were enrolled. 66 underwent lumpectomy and 31 underwent mastectomy. 16 had SLNB alone. There were no grade 3 acute toxicities meeting the primary toxicity endpoint. Common acute low-grade toxicities included fatigue (grade 1: 65 [66.3%]; grade 2: 7 [7.1%]), esophagitis (grade 1: 7 [7.1%]; grade 2: 10 [10.2%]), dermatitis (grade 1: 82 [83.7%]; grade 2: 7 [7.1%]). At median and maximum follow up of 8.02 (IQR: 3.31) and 13.3 years, respectively, there were 2 LRs (2.1%). 8-year DRFS, DFS and OS were 88.1% (95% CI 81.3%, 95.4%), 85.7% (95% CI 78.4%, 94.6%) and 90.5% (95% CI 84%, 97.6%), respectively. Clinician-rated cosmesis (n=64) was excellent/good in 67.2% of cases and fair/poor in 6.3%. Patient- rated cosmesis (n=47) was excellent/good in 91.5% and fair/poor in 8.5%, with patients rating themselves more favorably than their physicians (p=0.0014). The incidence of maximum grade 1, 2 and 3 late toxicities were 49 (62.8%), 15 (19.2%), and 3 (3.8%), respectively. This included 2 grade 3 asymmetries,1 grade 3 pigmentation change, and 1 grade 2 pneumonitis. There was no brachial plexopathy. Among the 28 patients who underwent reconstruction, 17 were implant-based and 11 were autologous. Of the implant-based, 9 underwent RT to the tissue expander and 8 to the permanent implant. 11/28 patients had long-term plastic surgery follow up. There were 3 hospitalizations with reoperation post-RT (1 unplanned revision, 1 implant removal for threatened exposure, and 1 excision of fat necrosis). There was 1 incident of wound infection/cellulitis. With regard to dosimetric constraints, 54.3% of plans (95% CI 43.6%, 64.8%) met all constraints. 92% (95% CI 83%, 97%), 98% (95% CI 93%, 100%) and 89% (95% CI 80%, 94%) met the PTV tumor V48Gy, PTV breast V40.5Gy, and PTV nodes V38.5Gy coverage constraints, respectively. Heart, contralateral lung, spinal cord, and esophagus constraints were met by all patients. 95% (95% CI 88.6%, 98.4%) met the ipsilateral lung V10Gy and 99% (95% CI 94%, 100%) met the thyroid contralateral lobe constraint. The BP constraint was met in 73% (95% CI 63.0%, 81.0%) of plans with a mean increase of 1.61 Gy (SD 1.96 Gy) over target. Conclusion Toxicity was low and outcomes were excellent in this prospective trial of hypofractionated regional nodal RT in the prone position. Dosimetric constraints were only met in 54% of plans with the nodal coverage and the BP constraint as the most frequently unmet. These constraints may need to be modified and/or techniques refined to optimize hypofractionated prone nodal RT. Citation Format: Juhi Purswani, Olivier Maisonet, Julie Xiao, Jose R Teruel, Christine Hitchen, Xiaochun Li, Judith D. Goldberg, Carmen A. Perez, Silvia C. Formenti, Naamit K. Gerber. A prospective phase I-II study of hypofractionated accelerated breast and nodal intensity modulated radiation therapy delivered in the prone position [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-22-05.

Abstract PO1-20-05: SURVIVE study – a multicenter, randomized, controlled phase 3 superiority trial, evaluating liquid biopsy guided intensified follow-up surveillance in women with intermediate-to high-risk early breast cancer

Abstract Background: Current guidelines limit routine breast cancer follow-up to clinical examinations and breast imaging. This is based on the results of two large cohort studies conducted in the 1980s that showed no improvement in overall survival (OS) by an intensified screening for distant metastases. Thus, imaging for distant metastases should currently only be performed in patients with specific symptoms. To detect distant relapse in a pre-symptomatic stage, we suggest the evaluation of a liquid biopsy-guided intensified surveillance, analyzing tumor markers (CA 27.29, CA 125 and CEA), circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA). Trial design: Funded by the German Federal Ministry of Education and Research, the SURVIVE study is the first large, randomized breast cancer surveillance trial to investigate the potential survival benefit of a liquid biopsy guided follow-up care in intermediate- to high-risk early breast cancer patients. The trial is a German multicenter, controlled phase 3 superiority study, in which 3500 patients are randomized in a 1:1 ratio to standard vs. liquid biopsy guided intensified follow-up care. At the time of writing 150 patients have been enrolled since December 2022. The total study duration is 144 months. Stratification factors are study site as well as HR-, HER2- and nodal status at surgery. Both study arms receive standard follow-up according to national guidelines. Additional blood samples (year 1-3 every 3 months, year 4-5 every 6 months) and standardized Quality of Life (QoL) questionnaires (EORTC-QLQ-C30/PA-F12, every 6 months) will be collected. While the standard surveillance arm samples will only be stored in a biobank, samples collected in the intensive surveillance arm will be tested for standard tumor markers, CTCs and ctDNA. Pre-specified abnormal findings of any of the liquid biopsy markers indicative of minimal residual disease trigger complete staging. In the event of confirmed disease recurrence, guideline-based treatment follows, otherwise, liquid biopsy testing continues. If applicable, study participants may enter interventional trials. Eligibility criteria: Eligible patients are adult females or males with histologically confirmed primary invasive intermediate to high-risk early breast cancer, defined as an indication for (neo-)adjuvant chemotherapy, and/or large tumor size ( > 50 mm), and/or positive lymph nodes (≥ pN1mi), and/or high grade (≥ G3). Primary anti-tumor therapy (surgery, adjuvant chemo- or radiotherapy) must have been completed ≤ 24 months (≤ 60 months for luminal carcinoma) previously. Patient enrollment during adjuvant endocrine- or antibody-therapy, CDK4/6-/PARP- or PI3K-inhibitors and antibody-drug conjugates is allowed. Statistical methods: The two primary objectives are to determine whether intensified, liquid biopsy-guided surveillance leads to better OS or an overall lead-time effect, compared to standard surveillance. The primary endpoint OS will be analyzed in the ITT population using Kaplan Meier methods and cox regression models, the overall lead time effect is a purely descriptive composite measure. Secondary objectives include invasive disease-free survival (IDFS), distant disease-free survival (DDFS), distant recurrence free survival (DRFS), breast cancer-specific survival (BCSS) and quality of life (QoL). Specific aims: To improve OS and the QoL during breast cancer follow-up, we propose a liquid biopsy guided follow-up method, with high sensitivity and specificity for the earlier detection of distant (oligo-)metastases, to enable earlier initiation of therapy. Conclusion: The SURVIVE-study is a long-awaited trial in early breast cancer follow-up, based on promising liquid biopsy markers. If successful, the results will lead to a paradigm shift in current follow-up care of intermediate to high-risk early breast cancer survivors. Clinical trial information: NCT05658172 Citation Format: Franziska Mergel, Sophia Huesmann, Thomas Friedl, Kerstin Pfister, Tatjana Braun, Angelina Fink, Forca Mehmeti, Tanja Fehm, Volkmar Müller, Klaus Pantel, Andreas Hartkopf, Elisabeth Wiesmüller, Brigitte Rack, Wolfgang Janni. SURVIVE study – a multicenter, randomized, controlled phase 3 superiority trial, evaluating liquid biopsy guided intensified follow-up surveillance in women with intermediate-to high-risk early breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-20-05.

Abstract PO4-19-01: The SURVIVE-HERoes trial – a secondary adjuvant treatment intervention study with trastuzumab-deruxtecan in patients with HER2 positive/HER2 low early breast cancer and a molecular relapse, based on a positive ctDNA result

Abstract Background: Despite current adjuvant treatment strategies, ≥ 20% of patients with early breast cancer (EBC) experience a metastatic relapse. In the new era of highly effective antibody drug conjugates (ADCs), secondary adjuvant treatment options for EBC patients at a high risk of relapse arise. The ADC trastuzumab-deruxtecan (T-DXd) has so far shown promising efficacy in patients with HER2-positive and HER2-low metastatic breast cancer (DESTINY Breast 03 and -04 trial) and is currently tested in the post-neoadjuvant setting in patients with non-pCR (DESTINY Breast 05 (TRUDY) trial). However, to successfully apply ADCs as a secondary adjuvant treatment, identification of patients who would benefit the most is required. The detection of minimal residual disease (MRD) using liquid biopsy, e.g. ctDNA, may offer a promising approach for patient selection. The efficacy of such a secondary adjuvant treatment in terms of delaying or even preventing distant metastases has yet to be evaluated in a randomized clinical trial. Trial design: The SURVIVE-HERoes trial is a prospective, randomized, open label comparative Phase III superiority trial in patients with intermediate to high-risk HER2-positive or HER2-low EBC, who participate in the large breast cancer surveillance trial SURVIVE (NCT05658172) and experience a molecular relapse as determined by a positive ctDNA result, but show no evidence of relapse or metastatic disease based on imaging by CT-scan and SPECT. In total, 180 patients will be enrolled and randomized with 2:1 allocation to treatment with T-DXd + (only endocrine therapy, if HR positive) versus standard of care (including endocrine treatment +/- CDK4/6-inhibitors or Neratinib). The treatment period lasts 12 months during which ctDNA levels will be repeatedly measured every 3 months (additional ctDNA testing will be performed at month 24 and 36). Stratification factors are HER2-, hormonal- and nodal status. Recruitment start is planned for Q1 2024. Eligibility criteria: Eligible patients are adult females/males, with HER2-positive or HER2-low EBC, as defined in the ASCO-CAP guidelines, and a positive ctDNA result (obtained in the SURVIVE study) that has to be confirmed ≤ 8 weeks before randomization. Primary anti-tumor therapy (surgery, adjuvant chemo- or radiotherapy) has to be completed ≥14 months, (postneo)-adjuvant treatment with anti-HER2-antibodies, T-DM1, Capecitabine, Pembrolizumab and Olaparib ≥ 4 weeks before randomization. Adequate bone marrow and cardiac function and no signs of ILD are mandatory. Statistics: The primary objective of SURVIVE-HERoes is the comparison of ctDNA clearance rates 6 months after randomization between the two study arms, which will be analysed using the chi square test for two independent proportions. Secondary objectives include the comparison of overall survival (OS), invasive disease-free survival (IDFS), distant disease-free survival (DDFS), distant recurrence-free survival (DRFS), breast cancer specific survival (BCSS), invasive breast cancer free survival (IBCFS) and quality of life (QoL) between the study arms as well as the safety and tolerability of T-DXd. Secondary survival endpoints will be estimated by the Kaplan Meier method and compared between the randomization arms using log-rank tests and cox regression models. Special aims: This trial is a proof of principle study with the aim to establish the efficacy of secondary adjuvant treatment with the ADC T-DXd in patients with HER2-positive/HER2-low early breast cancer, who are at high risk of relapse, as evidenced by detection of ctDNA in the blood. Conclusion: If SURVIVE-HERoes is successful, it could lead to a treatment shift towards early intervention with secondary adjuvant targeted therapies following liquid-biopsy based MRD detection. Contact: University Hospital Ulm, Dpt. Obstetrics & Gynecology, Germany, mail: studienzentrale.ufk@uniklinik-ulm.de Citation Format: Sophia Huesmann, Franziska Mergel, Kerstin Pfister, Angelina Fink, Forca Mehmeti, Peter Möller, Tanja Fehm, Volkmar Müller, Klaus Pantel, Thomas Friedl, Andreas Hartkopf, Brigitte Rack, Wolfgang Janni. The SURVIVE-HERoes trial – a secondary adjuvant treatment intervention study with trastuzumab-deruxtecan in patients with HER2 positive/HER2 low early breast cancer and a molecular relapse, based on a positive ctDNA result [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-19-01.

Abstract PO3-18-11: A011801 (CompassHER2 RD): Postneoadjuvant T-DM1 + tucatinib/placebo in patients with residual HER2-positive invasive breast cancer

Abstract Background: Patients with HER2+ early breast cancer (EBC) and invasive residual disease (RD) after neoadjuvant therapy (NAT) have a higher risk of relapse than patients who have a pathologic complete response (pCR). Escalation of therapy in patients with RD using post-neoadjuvant T-DM1 has become the new standard of care, leading to improved invasive disease-free survival (iDFS), but patients with estrogen receptor (ER)-negative or nodal RD have suboptimal outcomes, and central nervous system recurrences are a challenge. More effective treatment strategies are urgently needed. Alliance A011801 (CompassHER2 RD) is an escalation trial for patients with high-risk HER2+ RD after neoadjuvant systemic therapy, evaluating the addition of the HER2 selective tyrosine kinase inhibitor (TKI) tucatinib to post-neoadjuvant T-DM1. Methods: Eligibility and Intervention: Patients with high-risk HER2+ RD (i.e., ER-, node-positive, or both) after a predefined course of neoadjuvant HER2-directed treatment are randomized 1:1 to adjuvant T-DM1 + placebo, vs. T-DM1 and tucatinib with adjuvant RT +/- ET. Eligibility criteria include completion of ≥ 6 cycles of NAT, including ≥ 9 weeks of paclitaxel and trastuzumab +/- pertuzumab. All chemotherapy (CT) must be completed preoperatively unless participating in EA1181 (~15-30% will be participants in the CompassHER2 pCR de-escalation companion trial [NCT04266249]; these patients must receive postoperative CT to complete ≥ 6 cycles prior to enrollment on A011801). Patients who received prior HER2-targeted TKIs or antibody-drug conjugates are ineligible. Objectives: The primary objective is to determine if iDFS is improved with addition of tucatinib to T-DM1 in patients with HER2+ EBC with RD after neoadjuvant systemic therapy; secondary endpoints include overall survival, breast cancer free survival, distant recurrence-free survival, brain metastases-free survival and disease-free survival. Correlative objectives include the association of i) tumor infiltrating lymphocyte (TILs) levels in the primary tumor and RD with iDFS, ii) TILs with tucatinib benefit, iii) iDFS and circulating tumor cells (CTC) at serial timepoints and iv) the magnitude of benefit of tucatinib (iDFS) in patients with/without detectable pretreatment CTCs. Quality of life and pharmacokinetic endpoints are also being evaluated. Statistics: A011801 is a prospective, double-blind, randomized, phase III superiority trial; stratified by i) receipt of postoperative CT (Y/N), ii) hormone receptor-status (+/-), and iii) pathologic lymph node status (+/-). The study targets an absolute difference of 5% in iDFS (control vs. experimental arm 82% & 87%, HR = 0.7), with a two-sided alpha of 0.05 and power of 80%. The sample size is 981; target accrual = 1031 patients; activation and estimated completion dates are 01/6/21 and ~ 01/2028. Accrual as of 7/10/2023: 438 patients. Support: U10CA180821, U10CA180882; Seagen Inc; https://acknowledgments.alliancefound.org. ClinicalTrials.gov Identifier: NCT04457596 Citation Format: Ciara O'Sullivan, Karla Ballman, Linda McCall, Tyler Zemla, Anna Weiss, Melissa Mitchell, Victoria Blinder, Nadine Tung, William Irvin, Myounghee Lee, Sailaja Kamaraju, Matthew Goetz, W. Fraser Symmans, Virginia Borges, Ian Krop, Ann Partridge, Lisa Carey. A011801 (CompassHER2 RD): Postneoadjuvant T-DM1 + tucatinib/placebo in patients with residual HER2-positive invasive breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-18-11.

Abemaciclib in the Adjuvant Setting for Breast Cancer: A Systematic Review

The combination of adjuvant Abemaciclib with endocrine therapy (ET) has emerged as a significant advancement in the management of HR+, HER2-, node-positive, high-risk early breast cancer, as demonstrated by the findings of the MonarchE trial. This innovative treatment approach yielded not only statistically significant but also clinically meaningful improvements in invasive disease-free survival. Moreover, the benefits of this treatment combination were sustained over time, with a median follow-up of 27 months revealing continued clinically meaningful advantages in both invasive disease-free survival and distant recurrence-free survival. Importantly, these benefits extended beyond the initial 2-year treatment period, highlighting the durable efficacy of Abemaciclib and ET in preventing disease progression and distant metastasis. Furthermore, the safety profile of the combination therapy was found to be manageable and tolerable. This aspect is crucial for ensuring patient adherence to treatment and minimizing the burden of adverse effects. Overall, these findings underscore the potential of adjuvant Abemaciclib with ET as a valuable therapeutic option for patients with high-risk early breast cancer, offering both efficacy and tolerability in the long-term management of the disease. More studies are required, especially in the elderly, in order to know how to counteract diarrhea and to make Abemaciclib more tolerated.

Abstract PS06-06: Analysis of ctDNA for the detection of minimal residual disease (MRD) using a tissue-free, multiomic assay in patients with early-stage breast cancer

Abstract Background: The detection of ctDNA in patients with early-stage breast cancer after completion of adjuvant therapy is associated with a high risk of recurrence. Current clinical guidelines do not recommend routine screening for metastatic disease unless there are clinical signs and symptoms in patients who completed adjuvant therapy. However, ctDNA may serve as an early biomarker of recurrence which may allow effective identification of patients with asymptomatic distant metastases or molecular relapse only, who could benefit from early treatment intervention. Herein, we utilized a tissue-free, multiomic assay for the sensitive and specific detection of MRD in patients with early-stage breast cancer. Methods: Plasma samples were collected from patients with stage I-III breast cancer who were enrolled in the SUCCESS-A phase 3 clinical trial (NCT02181101) between 2006 and 2007. All patients received adjuvant chemotherapy +/- endocrine therapy and/or anti-HER2 therapy. Samples were collected approximately two years after completion of adjuvant chemotherapy, and plasma samples selected for analysis were from patients without evidence of disease recurrence prior to sample collection. Presence of MRD was assessed using Guardant Reveal powered by Infinity, which evaluates the epigenomic signals associated with cancer versus normal DNA for the detection of ctDNA. Samples with the presence of ctDNA are characterized for somatic alterations with common sources of interference such as clonal hematopoiesis excluded. An analytically validated bioinformatics pipeline was used for the detection of breast cancer ctDNA. Samples were analyzed blinded to the clinical data. Median survival times were estimated using the Kaplan-Meier method and hazard ratios were calculated based on univariable cox regression models. Results: A total of 311 plasma samples from 311 patients were evaluable. ctDNA was detected in 34% (13/38) of patients who subsequently developed distant recurrence and in none (0/7) of the patients who had local or contralateral breast cancer recurrence. ctDNA was detected in 60% (9/15) of samples that were collected within one year before recurrence. In the ctDNA detected samples from patients who had disease recurrence, the median time from sample collection to recurrence was 7.9 months (range, 1.4-28.6 months). ctDNA was detected in 6 patients who did not have a documented disease recurrence, resulting in a specificity of 97.7% (260/266). In the overall cohort, ctDNA detection was prognostic for recurrence-free survival (RFS; HR 11.0, 95% CI 2.28-53.6; p< 0.0001), distant recurrence-free survival (D-RFS; HR 13.7, 95% CI 2.52-74.9; p< 0.0001), and overall survival (OS; HR 17.4, 95% CI 1.33-227; p< 0.0001). Conclusion: Detection of ctDNA after adjuvant chemotherapy was highly prognostic and demonstrated high specificity in an early-stage breast cancer cohort. Larger, prospective studies are needed to confirm the prognostic value of ctDNA in the post-treatment setting and assess the clinical utility of MRD detection in this population. Citation Format: Wolfgang Janni, Thomas Friedl, Brigitte Rack, Peter A. Fasching, Andreas Hartkopf, Hans Tesch, Ralf Lorenz, Georg Heinrich, Jens-Uwe Blohmer, Tanja Fehm, Volkmar Müller, Andreas Schneeweiss, Matthias Beckmann, Matthias Ruebner, Nadia Harbeck, Klaus Pantel, Derek Dustin, Mingyang Cai. Analysis of ctDNA for the detection of minimal residual disease (MRD) using a tissue-free, multiomic assay in patients with early-stage breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS06-06.

Abstract PO4-27-07: A Phase 3, randomized, open-label study of upfront camizestrant vs standard endocrine therapy as adjuvant treatment for ER-positive/HER2-negative early breast cancer with intermediate-high or high risk of recurrence (CAMBRIA-2)

Abstract Background: Camizestrant is a next-generation oral selective estrogen receptor (ER) degrader and pure ER antagonist being investigated in early and advanced breast cancer (BC). In postmenopausal women with advanced ER-positive/human epidermal growth factor receptor 2 (HER2)-negative BC and disease recurrence or progression on or after ≤1 endocrine therapy (ET) in the advanced setting, camizestrant significantly prolonged progression-free survival compared with fulvestrant in the Phase 2 SERENA-2 trial. Camizestrant may also provide benefit in the early BC setting. Following locoregional therapy (surgery ± radiotherapy), standard adjuvant treatment of ET with or without chemotherapy and/or a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) has shown significant benefit in decreasing the risk of recurrence of stage I–III ER-positive/HER2-negative BC. However, BC recurrence as incurable metastatic disease is still common. Thus, adjuvant therapeutic options with improved clinical outcomes are needed. The CAMBRIA-2 study (NCT05952557) aims to assess whether upfront camizestrant can improve outcomes compared with standard ET as adjuvant treatment in patients with ER-positive/HER2-negative early BC with an intermediate-high or high risk of recurrence after definitive locoregional therapy. Trial design: This ongoing Phase 3, randomized, open-label study is enrolling women (pre-, peri-, or postmenopausal) and men with ER-positive/HER2-negative (HER2-negative status defined as immunohistochemistry 0, or 1+, or in situ hybridization-negative) early BC who are at intermediate-high or high risk of recurrence (as defined in the protocol) after having completed definitive locoregional therapy (surgery ± radiotherapy) ± (neo)adjuvant systemic chemotherapy, and who have no evidence of disease. Patients may have received up to 12 weeks of (neo)adjuvant ET prior to randomization. Patients are randomized (1:1) to receive camizestrant 75 mg ± abemaciclib ± luteinizing hormone-releasing hormone (LHRH) agonist or standard ET of the investigator’s choice (any aromatase inhibitor or tamoxifen) ± abemaciclib ± LHRH agonist for up to 7 years. The primary endpoint is invasive BC-free survival (IBCFS) (Standardized Definitions for Efficacy End Points [STEEP] 2.0 criteria). Secondary endpoints include invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) (STEEP 2.0 criteria), overall survival, safety, and health-related quality of life. Primary endpoint analysis will use a stratified log-rank test adjusting for stratification factors, assuming a two-sided significance level of 5%. Approximately 5500 patients will be randomized. Clinical trial identification: NCT05952557 Editorial acknowledgment: Writing assistance was provided by Clare Davis of BOLDSCIENCE Inc., funded by AstraZeneca. Legal entity responsible for the study: AstraZeneca Funding: This study was supported by AstraZeneca. Citation Format: Sibylle Loibl, Yeon Park, Sara Tolaney, Ioanna Gioni, Simon Johnston, Teresa Klinowska, Ingrid A. Mayer, Raquel Nunes, Barbara Pistilli, Mary Stuart, Angela Quintana, Andrew Walding, Michael Gnant. A Phase 3, randomized, open-label study of upfront camizestrant vs standard endocrine therapy as adjuvant treatment for ER-positive/HER2-negative early breast cancer with intermediate-high or high risk of recurrence (CAMBRIA-2) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-27-07.

Abstract PO2-18-09: A phase 3 randomized open-label study of extended adjuvant therapy with camizestrant vs standard endocrine therapy in patients with ER+/HER2– early breast cancer and an intermediate or high risk of recurrence (CAMBRIA 1)

Abstract Background: Definitive locoregional (surgery ± radiotherapy) and standard adjuvant endocrine therapy (ET) (± chemotherapy or cyclin-dependent kinase 4/6 inhibitor [CDK4/6i]) can achieve cure in many patients (pts) with estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER+/HER2–) early breast cancer (BC). Nevertheless, a significant proportion of pts with stage I–III disease will experience recurrence to metastatic, incurable disease (5- and 10-year cumulative incidences of recurrence of 8.3% and 14.0%, respectively). There is evidence that incorporating a more effective endocrine therapy after 2 years of standard adjuvant ET can result in clinical benefit for high-risk individuals. Camizestrant is a next-generation oral selective ER degrader and pure ER antagonist. In SERENA-2, camizestrant 75 mg and 150 mg significantly prolonged progression-free survival vs fulvestrant in postmenopausal women with ER+/HER2– advanced BC with disease recurrence or progression after ET. The CAMBRIA-1 study (NCT05774951) is evaluating the potential of extended adjuvant therapy with camizestrant to improve outcomes in pts with ER+/HER2– early BC with an intermediate or high risk of recurrence after definitive locoregional therapy and standard adjuvant ET. Trial design: This phase 3 randomized, open-label study is enrolling women (pre- or postmenopausal) and men with ER+/HER2– (immunohistochemistry 0/1+/2+/in situ hybridization-negative) early BC who have completed definitive locoregional therapy and standard adjuvant ET (± CDK4/6i) for ≥2 and ≤5 years (+ 3 months) without disease recurrence. Pts must be considered at intermediate or high risk of recurrence based on clinical, biological, and genomic factors. Pts are randomized (1:1) to continue standard ET of the investigator’s choice (tamoxifen or aromatase inhibitor ± luteinizing hormone-releasing hormone [LHRH] agonist) or camizestrant ± LHRH agonist for up to 60 months. The primary endpoint is invasive BC-free survival (STEEP 2.0 criteria). Secondary endpoints include invasive disease-free survival and distant relapse-free survival (STEEP 2.0 criteria), overall survival, safety, and health-related quality of life. Primary endpoint analysis will use a stratified log-rank test adjusting for stratification factors, assuming a two-sided significance level of 5%. Approximately 4300 pts will be randomized; enrollment is ongoing. Clinical trial identification: NCT05774951 Editorial acknowledgment: Writing assistance was provided by Alison Lovibond, PhD, of BOLDSCIENCE Inc., funded by AstraZeneca. Legal entity responsible for the study: AstraZeneca Funding: This study was supported by AstraZeneca. Citation Format: Erika Hamilton, Sibylle Loibl, Naoki Niikura, Priya Rastogi, Kamal S. Saini, Ioanna Gioni, Teresa Klinowska, Ingrid A. Mayer, Mary Stuart, Emilia Syta, Andrew Walding, Thomas Bachelot. A phase 3 randomized open-label study of extended adjuvant therapy with camizestrant vs standard endocrine therapy in patients with ER+/HER2– early breast cancer and an intermediate or high risk of recurrence (CAMBRIA 1) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-18-09.

Abstract PO4-26-04: Immunolocalization of cytoplasmic ER in ER-negative breast carcinoma as a potent favorable prognostic predictor

Abstract Background: It is known that estrogen receptor (ER) has extranuclear signaling functions in addition to classical genomic pathway, and estrogenic actions have been reported in ER-negative breast carcinoma cells. However, significance of cytoplasmic-ER immunoreactivity has not been reported in ER-negative breast carcinoma tissues. Methods: We immunolocalized cytoplasmic ER in 155 ER-negative breast carcinoma tissues and evaluated its clinicopathological significance including the prognosis. As a comparative cohort set, we also used 142 ER-positive breast carcinomas. Results: Cytoplasmic-ER immunoreactivity was detected in the carcinoma cells, but not in the non-neoplastic mammary epithelium. Cytoplasmic-ER immunoreactivity was positive in the 35 out of 155 (23%) ER-negative breast carcinoma cases, whereas it was detected only in 2 out of 142 (1.4%) ER-positive cases. Cytoplasmic ER status was positively associated with cytoplasmic-PR status, but inversely associated with Ki67 labeling index or distant free-relapse survival rate. Moreover, cytoplasmic-ER status turned out to be an independent good prognostic factor for both distant relapse-free survival and breast cancer specific survival. Conclusion: These findings suggested that cytoplasmic ER plays important roles in the ER-negative breast carcinoma, and cytoplasmic ER is a potent good prognostic factor. (accepted in Acta Histochemica et Cytochemica, 2023/Jun/27) Citation Format: Akiko Ebata, Takashi Suzuki, Narumi Harada-Shoji, Yohei Hamanaka, Minoru Miyashita, Erina Iwabuchi, Kiyoshi Takagi, Yasuhiro Miki, Hiroshi Tada, Takanori Ishida. Immunolocalization of cytoplasmic ER in ER-negative breast carcinoma as a potent favorable prognostic predictor [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-26-04.

Abstract PO1-03-03: STEEP criteria v2.0 validation: A multi-trial analysis using GEICAM and TRIO adjuvant trials to evaluate surrogate endpoints for overall survival

Abstract Background: Standardized definitions of efficacy endpoints are needed to improve clinical trial designs, data reporting and interpretation of results, and to allow cross-trial comparisons. STEEP (Standardized Definitions for Efficacy Endpoints) criteria were proposed in 2007 by an expert panel from the National Cancer Institute (NCI) to provide common definitions for clinical trials in early breast cancer (BC). Invasive disease-free survival (IDFS) was selected as a candidate surrogate endpoint for overall survival (OS) in adjuvant trials and has been widely used in the last 15 years. Advances in BC systemic treatment led to review these criteria (STEEP v2.0), with the definition of a new modified endpoint: invasive BC-free survival (IBCFS). IBCFS excludes second primary non-breast invasive cancers from IDFS which may better detect efficacy effects when the toxicity profile of the intervention is well-known and the risk of second primary cancer is small. Methods: We proposed a multi-trial analysis of 8 adjuvant chemotherapy (CT) trials from GEICAM and TRIO to evaluate the different surrogate endpoints defined in the STEEP v2.0. Trial-level surrogacy was assessed through correlation between the ln hazard ratio (HR) of OS and the ln HR of the different studied endpoints across trials. The correlation was estimated by the weighted, by trial size, least squares regression (WLS) line and evaluated comparing the R2 values between OS and the corresponding endpoint tested. Primary analyses evaluated the correlation of OS with IDFS/IBCFS. Secondary analyses evaluated the correlation of OS with other STEEP v2.0 endpoints (distant disease-free survival [DDFS], distant relapse-free survival [DRFS], recurrence-free survival [RFS], recurrence-free interval [RFI] and distant recurrence-free interval [DRFI]) and explored the surrogacy between OS and all endpoints in specific groups of patients (pts) according to their risk of relapse: hormone receptors positive (HR+)/HER2-negative (HER2-) pts with intermediate/high and high-risk and triple negative (TN) pts. Results: A total of 14,473 pts were included. Median age was 50 years (range, 20–82). All were female, and 51.8% were postmenopausal. With a median follow-up of 115 months (range, 0.0–188) we found 2,504 OS events, 4,146 IDFS events (60.9% being distant recurrences) and 3,810 IBCFS events (62.4% being distant recurrences). For each trial, HR of OS, IDFS and IBCFS indicated same conclusions. If HR< 1 for OS, it was also for IDFS and IBCFS and the same was true when HR >1. R2 results of the weighted linear correlations between the ln HR of OS versus (vs) IDFS and OS vs IBCFS were 0.86 and 0.89, respectively. Confidence intervals (CI) at 95% were both overlapping. All other efficacy endpoints showed strong correlation with OS in the overall analysis. R2 values for HR+/HER2- intermediate/high and high-risk pts were 0.89 (OS vs IDFS) and 0.84 (OS vs IBCFS). For TN pts the correlations were weaker, being 0.63 (OS vs IDFS) and 0.73 (OS vs IBCFS). All WLS R2 values are described in the table. Conclusions: All tested STEEP v2.0 endpoints were strongly correlated with OS (R2 close to 1), meaning that their use as surrogate endpoints for adjuvant CT trials is appropriate. Notably, no differences were found between them in this multi-trial analysis. Therefore, none of them is more appropriate than other to discriminate the value of a new intervention vs comparator in adjuvant CT studies with mature data and long-term follow-up. Table: Citation Format: Sara López-Tarruella, Marina Pollan, Ander Urriticoechea, Eva Carrasco, Gonzalo Spera, Miguel Martín, Begoña Bermejo, Linnea Chap, Manuel Ruíz - Borrego, John Crown, Jose Angel García-Sáenz, Arlene Chan, Angel Guerrero, Valerie Bee, Lourdes Calvo, Rodrigo Fresco, Andrea Blasco, Andrés Hernando, Dennis Slamon. STEEP criteria v2.0 validation: A multi-trial analysis using GEICAM and TRIO adjuvant trials to evaluate surrogate endpoints for overall survival [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-03-03.

Abstract PO4-17-12: Early adherence to adjuvant abemaciclib: Data from the Belgian Medical Need Program

Abstract Patient adherence profiles for adjuvant hormonal therapy combined with abemaciclib in HR+/HER2- High Risk EBC based on real world evidence (RWE) from a Medical Need Program in Belgium Background Following results of MonarchE, demonstrating clinically meaningful improvement in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS), a 2-year treatment with abemaciclib has been reimbursed in Belgium since May 1st, 2023 for the adjuvant treatment of HR+, HER2–, lymph node-positive (>3 or 1-3 if pT3 or grade 3) early breast cancer (EBC). In this trial, adverse event related treatment discontinuation was reported in 18,5% (8.9% after dose reduction) of which 10.1% in the first 5 months after starting this CDK 4/6 inhibitor. Prior to reimbursement, an early access program was initiated in Belgium on June 28 2022. We studied the proportion of patients estimated to be eligible for the program nationwide who effectively started adjuvant abemaciclib, as well as early treatment discontinuation and dose reductions. Methods The number of eligible patients for the adjuvant abemaciclib Medical Need Program (MNP) was estimated by the Belgian Cancer Registry based on the above mentioned reimbursement criteria for patients registered during the incidence year 2018. The MNP was active in Belgium from June 28 2022 until May 1 2023. Discontinuation rate and proportion with dose reductions were calculated using a nationwide prospective managed monthly updated register of participating patients including information on age at diagnosis, time since therapy start, delivered doses and patient reported adverse events (AE). They all signed an informed consent and agreed to share their registered data after anonymization. Data analysis was retrospective. Descriptive statistics were used. Results In this 10-month period, 840 patients were estimated to be eligible to receive adjuvant abemaciclib in Belgium. A total of 311 patients (309 women, 2 men) were included in the program, 37% of the estimated number of patients. Median age at initiation was 57 y. Median time on treatment was 4.5 months (156 patients >4.5 months on treatment). 21/311 (6.7%) patients discontinued (all causes). 2 patients never started. 10 patients (3.2%) discontinued their therapy without dose reduction. 12/311 (3.8%) had a starting dose of 2 × 100 mg/d. 128/311 (41.1%) had a dose reduction, 96/128 (75%) before 3 months of therapy. In the subgroup of 156 patients starting treatment >4.5 months ago, 16/156 (10.2%) discontinued treatment, 13 patients have not yet been reported. 79/156 (50.6%) required a dose reduction, of which 7 (4.5%) discontinued after dose reduction. The reasons for discontinuation reported: 8/21 (38%) gastro-intestinal intolerance, 3/21 (14.2%) real deterioration in renal function, 8/21 quality of life issues (not specified), 1/21 anal burning sensation and anal fistula, 3/21 asthenia and fatigue. Conclusion Of the estimated eligible patients in Belgium 37 % started with adjuvant abemaciclib. These results illustrate that there is a need to further improve implementation of adjuvant abemaciclib. Early results show that 89.8% of patients receiving adjuvant abemaciclib therapy in Belgium continued their treatment after 4.5 months and 50% of patients needed a dose reduction. Longer follow-up will be needed. Understanding the reasons of discontinuation and early dose adjustments can enable better patient support on adherence. This is a critical capability to ensure optimal patient compliance. Citation Format: Maxime Van Houdt, Marc Michaux, Sevilay Altintas, Ahmad Awada, Jean-Luc Canon, Hannelore Denys, François Duhoux, Guy Jerusalem, Jeroen Mebis, Rosanne Janssens, Isabelle Huys, Barbier Liese, Charlotte Verbeke, Sileny Han, Hans Wildiers, Patrick Neven. Early adherence to adjuvant abemaciclib: Data from the Belgian Medical Need Program [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-17-12.