Invasive Disease-free Survival Research Articles

Adjuvant treatment strategy evolution and risk stratification for hormone receptor-positive, human epidermal growth factor receptor-2 negative early breast cancer in China.

Patients with hormone receptor-positive (HR+), human epidermal growth factor receptor-2 negative (HER2-) early breast cancer (EBC) with high-risk clinicopathological features face an increased risk of recurrence. This study explored the evolving treatment landscape and clinical outcomes in patients with EBC using a nationwide database. The study cohort comprised HR+/HER2-, stages 1-3, patients with EBC who underwent surgery and received adjuvant endocrine therapy (AET) from January 2013 to March 2021. High-risk patients were defined by ≥4 positive axillary lymph nodes, or 1-3 positive lymph node(s) with at least one high-risk feature (histologic grade 3, tumor size ≥5cm, or Ki-67 ≥20%). A low-risk cohort included patients not meeting the criteria. Survival analysis was conducted with a cutoff of September 2021. The study included 4088 eligible patients (1310 high-risk patients and 2778 low-risk patients). High-risk patients were more likely to receive adjuvant chemotherapy and radiotherapy compared to low-risk patients. From 2013 to 2021, an increasing proportion of patients received aromatase inhibitors and ovarian function suppression as part of their AET. The 2-, 5-, and 7-year invasive disease-free survival for high-risk cohort were 90.67%, 75.26%, and 57.10%, respectively, these rates were notably higher for low-risk cohort at 97.14%, 89.85%, and 84.83%. High-risk patients demonstrated a higher risk of recurrence or death compared with low-risk patients (hazard ratio, 2.38; 95% CI, 1.82-3.12). In the setting of standard or even intensive AET, patients with EBC with high-risk features still present high recurrence risk, highlighting the urgent need for innovative adjuvant treatment strategies.

A 10-Gene Signature to Predict the Prognosis of Early-Stage Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a particularly challenging subtype of breast cancer, with a poorer prognosis compared to other subtypes. Unfortunately, unlike luminal type cancers, there is no validated biomarker to predict the prognosis of patients with early-stage TNBC. Accurate biomarkers are needed to establish effective therapeutic strategies. In this study, we analyzed gene expression profiles of tumor samples from 184 TNBC patients (training cohort, n=76; validation cohort, n=108) using RNA sequencing. By combining weighted gene expression, we identified a 10-gene signature (DGKH, GADD45B, KLF7, LYST, NR6A1, PYCARD, ROBO1, SLC22A20P, SLC24A3, and SLC45A4) that stratified patients by risk score with high sensitivity (92.31%), specificity (92.06%), and accuracy (92.11%) for invasive disease-free survival. The 10-gene signature was validated in a separate institution cohort and supported by meta-analysis for biological relevance to well-known driving pathways in TNBC. Furthermore, the 10-gene signature was the only independent factor for invasive disease-free survival in multivariate analysis when compared to other potential biomarkers of TNBC molecular subtypes and T-cell receptor β diversity. 10-gene signature also further categorized patients classified as molecular subtypes according to risk scores. Our novel findings may help address the prognostic challenges in TNBC and the 10-gene signature could serve as a novel biomarker for risk-based patient care.

Oncologic Outcomes for Different Axillary Staging Techniques in Patients with Nodal-Positive Breast Cancer Undergoing Neoadjuvant Systematic Treatment: A Cancer Registry Study.

Targeted approaches such as targeted axillary dissection (TAD) or sentinel lymph node biopsy (SLNB) showed false-negative rates of < 10% compared with axillary lymph node dissection (ALND) in patients with nodal-positive breast cancer undergoing neoadjuvant systemic treatment (NAST). We aimed to evaluate real-world oncologic outcomes for different axillary staging techniques. We identified nodal-positive breast cancer patients undergoing NAST from 2016 to 2021 from the state cancer registry of Baden-Wuerttemberg, Germany. Invasive disease-free survival (iDFS) was assessed using Kaplan-Meier statistics and multivariate Cox regression models (adjusted for age, ypN stage, ypT stage, and tumor biologic subtype). A total of 2698 patients with a median follow-up of 24.7 months were identified: 2204 underwent ALND, 460 underwent SLNB (255 with ≥ 3 sentinel lymph nodes [SLNs] removed, 205 with 1-2 SLNs removed), and 34 underwent TAD. iDFS 3 years after surgery was 69.7% (ALND), 76.6% (SLNB with ≥ 3 SLNs removed), 76.7% (SLNB with < 3 SLNs removed), and 78.7% (TAD). Multivariate Cox regression analysis showed no significant influence of different axillary staging techniques on iDFS (hazard ratio [HR] for SLNB with < 3 SLNs removed 0.96, 95% confidence interval [CI] 0.62-1.50; HR for SLNB with ≥ 3 SLNs removed 0.86, 95% CI 0.56-1.3; HR for TAD 0.23, 95% CI 0.03-1.64; ALND reference), and for ypN+ (HR 1.92, 95% CI 1.49-2.49), triple-negative breast cancer (HR 2.35, 95% CI 1.80-3.06), and ypT3-4 (HR 2.93, 95% CI 2.02-4.24). These real-world data provide evidence that patient selection for de-escalated axillary surgery for patients with nodal-positive breast cancer undergoing NAST was successfully adopted and no early alarm signals of iDFS detriment were detected.

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&amp;lt; 1 for OS, it was also for IDFS and IBCFS and the same was true when HR &amp;gt;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 PO3-02-05: Racial and Ethnic Differences in Clinical Outcomes among North American Patients with Hormone Receptor-Positive, HER2-negative, Early Breast Cancer in the PALLAS Trial (AFT-05)

Abstract Introduction: Analyses of multiple clinical trials have suggested racial and ethnic disparities in outcomes for early-stage, hormone receptor-positive and HER2-negative (HR+HER2-) breast cancer, however, none of these studies examined the use of adjuvant CDK4/6 inhibitors. The objective of this study was to explore racial and ethnic differences in toxicity, treatment duration, and disease outcomes in patients (pts) with early-stage HR+HER2- breast cancer treated with or without adjuvant palbociclib on the PALLAS trial. Methods: The PALLAS phase III, global, open-label trial randomized 5,796 pts with stage II-III HR+HER2- breast cancer to 2 years of palbociclib plus ongoing provider/patient choice adjuvant endocrine therapy (ET+palbo) vs. ET alone (ET). The analytic cohort was limited to pts enrolled in North America with known self-reported race and ethnicity (Non-Hispanic White, Non-Hispanic Black, Hispanic, Asian or Pacific Islander). Descriptive statistics were used to examine treatment characteristics, early discontinuation, and toxicity by race and ethnicity. Kaplan-Meier curves were used to estimate 3-year locoregional recurrence-free survival (LRFS) and invasive disease-free survival (IDFS) stratified by racial and ethnic group. Cox proportional hazards models were used identify predictors of LRFS and IDFS. Results: 2,547 North American pts were randomized and included in the intent-to-treat population with a median follow-up of 59.8 months; 1,996 (78.4%) identified as Non-Hispanic White (NHW), 132 (5.2%) Non-Hispanic Black (NHB), 156 (6.1%) Hispanic, and 134 (5.3%) Asian or Pacific Islander (API). Stage, performance status, type of surgery, and prior radiation were similar across racial and ethnic groups. Age, body mass index, grade, and prior chemotherapy differed by race and ethnicity (p&amp;lt; 0.05). Median age was lowest in API pts and highest in NHW pts (47.5 vs 53.0 years, respectively). Median body mass index was lowest in API and highest in NHB pts (24.4 vs 30.9). NHB pts were most likely to have high-grade disease (40.9% vs 26.9-30.5% in other groups). NHW pts were least likely to have received prior chemotherapy (81.0% vs 87.1-91.0%). Palbociclib early discontinuation was lowest in NHB pts (50.7%) and highest in Hispanic pts (65.9%), p=0.14. ET early discontinuation was similar across all groups (p=0.35). Palbociclib grade 3-4 overall toxicity was variable across groups (NHW 71.6%, NHB 79.1%, Hispanic 69.5%, API 85.2%), but this variation did not reach statistical significance (p=0.07). Neutropenia was highest in API pts (90.0% vs 57.3% in NHW, 58.2% in NHB, and 51.2% in Hispanic pts, p&amp;lt; 0.01). Overall 3-year LRFS was 98% (95% CI 97-98%) and IDFS was 89% (95% CI 88-90%). LRFS and IDFS were statistically similar by race and ethnicity and within each study arm (Table). No differences in LRFS or IDFS were seen by race or ethnicity in adjusted models (p=0.95). Conclusions: In this clinical trial population of HR+HER2- breast cancer patients exposed to similar treatments, no racial/ethnic differences were seen in short-term LRFS or IDFS across study arms. Differences in palbociclib toxicity by racial and ethnic group, particularly neutropenia, were seen with the highest toxicity in API patients; however, this difference did not translate into early discontinuation of palbociclib or ET. Table: 3-year Kaplan-Meier Survival Outcomes Stratified by Race and Ethnicity Citation Format: Olga Kantor, Oluwadamilola (Lola) Fayanju, Amylou Dueck, Michael Gnant, Harold Burstein, Matthew Goetz, Claudine Isaacs, Lois Shepherd, Olwen Hahn, Daniel Anderson, Kathy Miller, Hope Rugo, Tiffany Traina, Zoneddy Dayao, Katherine Clifton, Eric Winer, Antonio Wolff, Norman Wolmark, Dongrui Lu, Patrick O'Brien, Sara Scovil, Angela DeMichele, Erica Mayer. Racial and Ethnic Differences in Clinical Outcomes among North American Patients with Hormone Receptor-Positive, HER2-negative, Early Breast Cancer in the PALLAS Trial (AFT-05) [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 PO3-02-05.

Abstract PO3-17-05: Clinical Characteristics and Outcomes of Patients Receiving Adjuvant Paclitaxel and Trastuzumab (APT regimen) for HER2-Positive Early-Stage Breast Cancer in Brazil: A Real-World Evidence

Abstract Introduction: The APT trial established adjuvant paclitaxel and trastuzumab (TH) as the standard of care for HER2-positive early-stage breast cancer with tumor size ≤ 3 cm and no more than one lymph-node micrometastasis. This single-arm phase II trial demonstrated favorable long-term outcomes, with a 3-year invasive disease-free survival (IDFS) rate of 98.7% (95% CI 97.6 – 99.8%). In an updated follow-up analysis, the 10-year IDFS and overall survival (OS) rates were 91.3% (95% CI 88.3 – 94.4%) and 94.3% (95% CI 91.8 – 98.3%), respectively. Nevertheless, outcomes observed in real-world scenarios have frequently been less favorable than those observed in clinical trials. We aimed to characterize the population receiving the APT regimen in clinical practice and evaluate if real-world outcomes align with those observed in the pivotal clinical trial. Methods: This retrospective cohort study included patients with HER2-positive early-stage breast cancer treated between 2015 and 2023 at four Brazilian cancer institutions, including public and private hospitals. Clinical and demographic data, treatment details, and outcomes were collected from electronic records. The primary endpoints were the 3-year and 7-year invasive disease-free survival (IDFS) rates. Secondary endpoints included overall survival (OS) and factors associated with IDFS. Survival analysis employed the Kaplan-Meier method, and Cox regression assessed prognostic factors. Results: A total of 133 patients treated with the APT regimen were evaluated, with a median age of 56 years (range 20–83). The majority had no special type breast carcinoma (92.4%), grade 2 (63.4%) or grade 3 (34.3%) tumors, no angiolymphatic invasion (76.3%), positive estrogen receptor (69.9%), positive progesterone receptor (55.6%), and node-negative disease (94.7%). Tumor staging distribution was as follows: T1a (12%), T1b (23.3%), T1c (49.6%), and T2 (13.5%). Most patients (95.4%) received the APT regimen as per guideline recommendations, while 3.8% received it due to contraindication to other therapies. With a median follow-up of 45.8 months, 8 patients (5.8%) experienced an invasive disease event or death from any cause: 5 (3.8%) had distant recurrence, 1 (0.8%) had local recurrence, and 2 (1.5%) died without recurrence. Notably, these events occurred in patients receiving the APT regimen according to standard indications, except for one patient with N+ disease and a contraindication to another regimen. The recurrence rate according to the T stage is presented in the Table. The 3-year IDFS rate was 100% (95% CI not applicable). All events occurred after the 3-year time point, resulting in a 7-year DFS rate of 80.8% (95% CI 62.7–90.7%). No prognostic factors related to IDFS were identified. Four patients died during the study period, yielding a 7-year OS rate of 88.0% (95% CI 61.6–96.6%). Conclusion: While the baseline characteristics of this cohort resembled those of the APT trial, the long-term outcomes observed in the real-world setting were less favorable. Further investigation is required to determine the reasons for this discrepancy, underscoring the necessity for larger real-world data studies to validate these findings. Recurrence rate according to T stage XX XX Citation Format: Giselle Carvalho, Renata Colombo Bonadio, Pedro Bergmann, Marina Nishimuni, André Rossi, Cristiano Souza, Gabriel Guimarães, Laura Testa, José Bines. Clinical Characteristics and Outcomes of Patients Receiving Adjuvant Paclitaxel and Trastuzumab (APT regimen) for HER2-Positive Early-Stage Breast Cancer in Brazil: A Real-World Evidence [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 PO3-17-05.

Abstract PS09-04: The benefit of adjuvant pertuzumab and trastuzumab according to estrogen receptor and HER2 expression: sub-analysis of the APHINITY trial

Abstract Background: Some studies suggest that response to HER2-targeting agents may differ according to estrogen receptor (ER) and HER2 expression levels. This study aimed to investigate the magnitude of benefit from the addition of pertuzumab to trastuzumab and chemotherapy according to ER and HER2 expression levels in the APHINITY trial. Methods: APHINITY (NCT01358877; BIG 4-11) was a randomized, double-blind, phase III study comparing the addition of pertuzumab or placebo to adjuvant trastuzumab and chemotherapy in an ITT population of 4804 patients with HER2-positive early breast cancer. The primary objective of this exploratory, unplanned analysis was to compare whether the addition of pertuzumab to trastuzumab had an impact in invasive disease-free survival (IDFS) within different subgroups defined by HER2 FISH amplification ratio and/or ER percentage of positivity on immunohistochemistry (IHC) (centrally assessed). Patients with a FISH ratio less than 2 were excluded from this analysis, leaving 4782 patients. IDFS was defined as the time from randomization until the date of the first occurrence of an IDFS event. HER2 FISH amplification ratio was categorized as low (2≤ FISH ratio &amp;lt; 5) vs. high (FISH ratio ≥5). ER expression on IHC was categorized as negative ( &amp;lt; 1%) vs. positive (≥1%). A subgroup analysis using Cox proportional hazards regression models was used to model IDFS, assessing four categories formed by cross classifying the FISH ratio and ER groups. The model was adjusted for randomized arm, adjuvant chemotherapy regimen received, and a combined variable of nodal status and protocol version. Results: The 4782 patients had a median age of 51 years old (IQR 44-59), with a median follow up time of 73.6 months (IQR 63.0-75.2). Most patients received an anthracycline-based chemotherapy (n=3712, 77.6%). ER expression was positive in 3047 patients (63.7%). HER2 FISH amplification ratio was high in 2479 patients (51.8%). All FISH ratio/ER subgroups seem to derive IDFS benefit from the addition of pertuzumab (HR &amp;lt; 1) (Table 1). The HER2 FISH ratio-low/ER positive subgroup had the largest reduction in risk of an IDFS event, 30% for the pertuzumab arm (HR=0.70, 95% CI 0.51-0.95) versus placebo. Smaller differences in IDFS events were observed between the treatment arms in the other subgroups. The subgroup of tumors with HER2 FISH ratio-high/ER-negative expression showed the numerically smallest benefit in IDFS events with the addition of pertuzumab (HR 0.85, 95% CI 0.59-1.25), see Table 1. Conclusions: In this APHINITY sub-analysis, patients treated with pertuzumab/trastuzumab derive similar benefit regardless of ER and HER2 expression levels. More research is needed to find predictive biomarkers to escalate or de-escalate treatments. Table 1. Abbreviations: FISH: fluorescence in situ hybridization, ER: estrogen receptor; IDFS: invasive disease-free survival; CI: confidence interval; HR: hazard ratio Citation Format: Evandro de Azambuja, Elisa Agostinetto, Faye Samy, Serena Di Cosimo, Philippe Aftimos, Noam Pondé, Daniel Eiger, Matteo Lambertini, David Cameron, Astrid Kiermaier, Andrew Bailey, Giuseppe Viale, Sherene Loi, Martine Piccart. The benefit of adjuvant pertuzumab and trastuzumab according to estrogen receptor and HER2 expression: sub-analysis of the APHINITY 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 PS09-04.

Abstract GS03-12: Phase III study of adjuvant ado-trastuzumab emtansine vs trastuzumab for residual invasive HER2-positive early breast cancer after neoadjuvant chemotherapy and HER2-targeted therapy: KATHERINE final IDFS and updated OS analysis

Abstract Background: Patients with HER2-positive early breast cancer (EBC) who have residual invasive disease after neoadjuvant chemotherapy + HER2-targeted therapy have a high risk of recurrence and death. The standard of care when KATHERINE was designed was continuation of the same HER2-targeted therapy in the adjuvant setting for 1 year. The primary analysis of KATHERINE in 2018 showed that the risk of recurrence of invasive BC or death was 50% lower with adjuvant ado-trastuzumab emtansine (T-DM1) than with trastuzumab. Methods: KATHERINE (NCT01772472/BO27938/NSABP B-50-I/GBG 77) is a phase III, open-label, global study of patients with centrally confirmed, HER2-positive (immunohistochemistry 3+ or in situ hybridization-positive) primary BC (T1–4, N0–3, M0) who received neoadjuvant chemotherapy + HER2-targeted therapy, which had to include a taxane and trastuzumab, followed by surgery, with pathologically documented residual invasive disease in the breast and/or axillary lymph nodes. Within 12 weeks of surgery, patients were randomized 1:1 to T-DM1 (3.6 mg/kg intravenously [IV] every 3 weeks [q3w]) or trastuzumab (6 mg/kg IV q3w) for 14 cycles. Randomization was stratified by clinical stage at presentation, hormone receptor status, single vs dual neoadjuvant HER2-targeted therapy, and pathologic nodal status after neoadjuvant therapy. Patients received radiotherapy and/or endocrine therapy per local standards. The primary endpoint was invasive disease-free survival (IDFS). We report the final IDFS analysis, which was to occur after ~384 events had been reported, and the preplanned second interim analysis of overall survival (OS); specified to occur at the same time. Results: With a median follow-up of 8.4 years (101 months), T-DM1 sustained the improvement in IDFS over trastuzumab (unstratified hazard ratio [HR] 0.54; 95% confidence interval [CI] = 0.44, 0.66; p &amp;lt; 0.0001). Landmark 7-year IDFS rates were increased from 67.1% with trastuzumab to 80.8% with T-DM1; a difference of 13.7%. At clinical cutoff for the final IDFS analysis, 215 deaths had been reported. T-DM1 significantly reduced the risk of death by 34% compared with trastuzumab (unstratified HR 0.66; 95% CI = 0.51, 0.87; p = 0.0027). Deaths had occurred in 89/743 patients (12.0%) in the T-DM1 arm and 126/743 (17.0%) in the trastuzumab arm. Landmark 7-year OS rates were increased from 84.4% with trastuzumab to 89.1% with T-DM1; a difference of 4.7%. OS and IDFS benefits were seen across key subgroups. A low incidence of adverse events (AEs) related to study treatment or to study procedures was observed during the post-treatment period: Grade ≥3 related AEs occurred in 3/740 patients (0.4%) in the T-DM1 arm and 3/720 (0.4%) in the trastuzumab arm; serious related AEs, in 2/740 (0.3%) and 4/720 (0.6%), respectively. Related AEs classed as “cardiac disorders” were rare in both arms with extended follow-up. Conclusions: After 8.4 years (101 months) median follow-up, T-DM1 significantly improved OS in patients with HER2-positive EBC with residual invasive disease after neoadjuvant therapy. The IDFS benefit of T-DM1 was sustained in the intention-to-treat population with longer follow-up, and no new safety issues emerged. Cardiac toxicity was rare in both arms. T-DM1 is the first therapy to show improved survival post-surgery in patients with HER2-positive EBC with residual invasive disease after neoadjuvant therapy. Follow-up is ongoing for the final OS analysis. Citation Format: Sibylle Loibl, Max Mano, Michael Untch, Chiun-Shen Huang, Eleftherios Mamounas, Norman Wolmark, Adam Knott, Asna Siddiqui, Thomas Boulet, Beatrice Nyawira, Eleonora Restuccia, Charles Geyer. Phase III study of adjuvant ado-trastuzumab emtansine vs trastuzumab for residual invasive HER2-positive early breast cancer after neoadjuvant chemotherapy and HER2-targeted therapy: KATHERINE final IDFS and updated OS analysis [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 GS03-12.

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 &amp;gt;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 PO5-17-08: Real world outcomes of neoadjuvant chemotherapy in ER-positive/PR-positive, HER2-negative breast cancer

Abstract Background: Neoadjuvant chemotherapy is utilized to downstage locally-advanced estrogen receptor-positive (ER+)/progesterone receptor-positive (PR+), HER2-negative breast cancer despite modest pathological complete response (pCR) rates. The two most commonly utilized regimens include docetaxel plus cyclophosphamide (TC) or dose-dense doxorubicin and cyclophosphamide followed by paclitaxel (ddAC-T). Given few head-to-head comparisons of neoadjuvant TC with ddAC-T in this population, we performed a real world data analysis. Methods: 148 patients with ER+/PR+, HER2-negative breast cancer were included in the analysis. The patients were divided into two groups based on the neoadjuvant chemotherapy regimen used (TC vs ddAC-T) and the clinical responses to chemotherapy were categorized as complete, partial, no response/stable, or progressive disease. We examined the differences or associations in demographics, clinical characteristics, overall survival (OS), and invasive disease-free survival (IDFS) between TC and ddAC-T neoadjuvant chemotherapy. pCR was defined as the absence of invasive carcinoma in breast and lymph nodes (ypT0/ypTis and ypN0). Partial response was defined as a decrease in either or both T and/or N stage, compared to pre-treatment evaluation; no response was defined as no change in either T or N categories; and progressive disease was defined as an increase in either the T or N staging at time of pathologic evaluation. Results: The median age of participants was 55 years (range 28-78 years). 67% had clinical stage II disease, while 26% had stage III. 130 participants received neoadjuvant ddAC-T while 18 participants received TC. The ddAC-T group had 7% patients who achieved a pCR and 37% with a partial response, compared to the TC group with 0% of patients with a pCR and 33% with a partial response. The TC group had a higher rate of progressive disease, compared to the ddAC-T group (67% versus 20%). On univariate analysis, the choice of neoadjuvant chemotherapy was not predictive of pathologic response (p = 0.3864). As expected, premenopausal status was associated with a higher likelihood of a pathologic response with an odds ratio of 2.917 (95% CI: 1.465-5.809). On multivariate analysis, chemotherapy regimen was not predictive of pathologic response (p = 0.6047), after controlling the effects of age and menopausal status. No significant difference was noted in OS or IDFS at 24 and 48 months between the ddAC-T and TC groups. On multivariate analysis, controlling for BMI, ER, PR, race, and ECOG performance status, the choice of chemotherapy was not predictive of IDFS. Non-white participants appeared to have inferior IDFS (HR = 2.956, 95% CI: 1.208, 7.238, p-value = 0.0177). Conclusion: In this single-center retrospective analysis, we show real world outcomes of the use of neoadjuvant chemotherapy regimens among patients with ER+/PR+, HER2-negative breast cancer. Both ddAC-T and TC had low pCR rates, 5.98% and 0%, respectively. However, there was no statistical difference between IDFS or OS when comparing the two chemotherapy regimens. More data are needed to optimize neoadjuvant treatment in this patient population and to determine whether anthracyclines can be avoided. Table. Pathologic responses The results (summarized by odds ratio (OR) and its 95% CI) from logistic regression on the pathological responses (complete and partial). Citation Format: Matthew Kurian, Marcus Trybula, Kanchi Patell, Gregory Guzik, Seunghee Margevicius, Pingfu Fu, Alberto Montero, James Martin. Real world outcomes of neoadjuvant chemotherapy in ER-positive/PR-positive, HER2-negative 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 PO5-17-08.

Abstract PO5-19-10: First oncological outcomes of HypoG-01: a UNICANCER phase III trial comparing loco-regional hypo vs normo fractionated radiation therapy in early breast cancer patients

Abstract Objective Normofractionated (NF) radiation therapy (RT) is still standard for loco-regional early breast cancer (EBC) in many countries. HypoG-01, a UNICANCER, non-inferiority, open-label, multicenter, randomized phase III trial (NCT03127995), conducted in parallel with the DBCG Skagen trial 1 (NCT02384733), evaluated hypofractionated (HF) RT with 40 Gy/15 fr (2.67 Gy/fr) versus NF RT 50 Gy/25 fr (2.0 Gy/fr). This is the first report of oncological outcomes, secondary endpoints of the trial. Methods Patients (pts) ≥18 years old were operated for T1-3, N0-3, M0 breast cancer. All pts received nodal and thoracic wall or breast RT. Tumor-bed boost (sequential or simultaneous) and nodal levels treated were decided according to local guidelines. Target volumes were delineated according to the ESTRO consensus. RT technique was left at the investigator’s discretion. Stratification factors included treating center, type of surgery, number of positive nodes and body mass index. The primary endpoint, reported previously, was time to occurrence of arm lymphedema. Oncological outcomes included locoregional relapse free survival (LRFS), invasive disease-free survival (IDFS), distant disease-free survival (DDFS), breast cancer specific survival (BCSS) and overall survival (OS) as defined per DATECAN guidelines. All time to cancer related endpoints were defined as starting from the date of randomization until the event. The primary statistic test was stratified one-sided logrank test: 5% significance level in per-protocol population (PPP) with a pre-specified non-inferiority margin of 1.545. Stratified Cox model was used for calculating hazard ratios of oncological outcomes. Results In total, 1265 pts were randomized to HF versus NF RT from Sep 2016 to Mar 2020 with 1221 in the PPP (HF group 614 pts (50.3%); NF group 607 (49.7%)), 5 consent withdrawn and 39 major deviations. Median age was 58 years (range 23-91), surgery included mastectomy (501 pts; 45%) and axillary clearance (921 pts; 82.8%). Sequential (67.8%) or simultaneous integrated (32.2%) tumor-bed boost was used in 596 pts (48.8%). With a median follow-up for OS in PP analysis of 3.8 years (95% CI 3.3 to 3.9), HF was non-inferior to NF RT in terms of lymphedema (HR=1.07; 90% CI 0.86-1.34, non-inferiority p=0.003). Table 1 reports the hazard ratio and 3-year survival rates for the oncological endpoints LRFS, IDFS, DDFS, BCCS and OS. There was no sign of disadvantage for any of these endpoints comparing HF to NF. Additional analyses will be presented at the meeting. Conclusion Moderately HF loco-regional RT is non-inferior to NF RT in terms of lymphedema risk in EBC and does not show a disadvantage in terms of LRFS, IDFS, DDFS, BCCS and OS with a median follow-up of 3.8 years. Together with the Skagen 1 trial, this study provides level 1A evidence supporting the use of 40 Gy/15 fr for loco-regional radiation therapy in EBC with respect to arm lymphedema risk; Table 1: Oncological outcomes according to treatment arm in the per protocol analysis HF: Moderately hypofractionated radiation therapy; NF: Normofractionated radiation therapy; n:number of patients; N: number of events Citation Format: Sofia Rivera, Eleni Karamouza, Youlia Kirova, Séverine Racadot, Mohamed Benchalal, Jean-Baptiste Clavier, Claire Charra-Brunaud, Marie-Eve Chand-Fouche, Delphine Argo-Leignel, Karine Peignaux, Ahmed Benyoucef, David Pasquier, Philippe Guilbert, Julien Blanchecotte, Agnès Tallet, Adeline Petit, Guillemette Bernadou, Xavier Zasadny, Claire Lemanski, Jacques Fourquet, Emmanuelle Malaurie, Honorine Kouto, Carole Massabeau, Alexandre Henni, Pauline Regnault, Aurélie Belliere, Yazid Belkacemi, Magali Le Blanc-Onfroy, Julien Geffrelot, Jean-Briac Prevost, Marie Bergeaud, Assia Lamrani-Ghaouti, Amandine Ruffier, Naima Bonnet, Stephanie Wong, Christine Rossier, Thomas Brion, Pierre Maroun, Claire Petit, Guillaume Auzac, Stefan Michiels. First oncological outcomes of HypoG-01: a UNICANCER phase III trial comparing loco-regional hypo vs normo fractionated radiation therapy in early breast cancer patients [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 PO5-19-10.

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&amp;lt; 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 &amp;lt; 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 PO1-17-07: Invasive disease-free survival as a surrogate for overall survival in patients with hormone receptor−positive/human epidermal growth factor receptor 2−negative early breast cancer: a real-world analysis

Abstract Background: Although the goal of treatment is to improve overall survival (OS), in the adjuvant setting, disease-free survival (DFS) is an important endpoint because DFS risk reduction may reduce mortality risk. After introduction of the STEEP criteria, invasive DFS (iDFS) was adopted as an objective, well accepted primary endpoint in early breast cancer (EBC) trials. This analysis evaluated iDFS as a surrogate for OS in the HR+/HER2− EBC adjuvant treatment setting using real-world data. Methods: This retrospective analysis of the ConcertAI Patient360 database contains deidentified electronic medical records of patients (pts) treated at US academic and community oncology clinics from Jan 1, 1995 to Apr 30, 2021. The cohort included pts with AJCC (8th ed.) stage II-III (if IIIB or IIIC, confirmation was required on residual tumor status; pathological and/or clinical staging [pathological stage was prioritized if both existed in the record]) HR+/HER2− EBC who had surgery and initiated adjuvant endocrine therapy (ET); ovarian function suppression was permitted. iDFS (disease recurrence, metastasis, second primary tumor, or death) and OS (death due to any cause) were defined as time between ET start and first qualifying event. Pts not experiencing an event were censored at data cutoff or maximum follow-up (whichever was first) for iDFS and maximum follow-up for OS. Correlation analyses between individual iDFS and OS times were performed using Pearson and Spearman correlations and an iterative multiple imputation (IMI) algorithm. Subgroup analyses were conducted by first ET, menopausal status (imputed as 50 years if missing), stage, nodal status, prior (neo)adjuvant chemotherapy, and prior radiation. Results: In total, 3133 pts were analyzed. Mean (SD) age (index or ET initiation date) was 58.4 (12.4) years; 98.8% of pts were female, 29.9% were premenopausal, 80.9% had stage II disease, 57.1% had nodal involvement, and 41.6% and 48.8% had received (neo)adjuvant chemotherapy and radiation therapy. Overall, 1854 and 653 pts received nonsteroidal aromatase inhibitors and tamoxifen only. The median follow-up time was 55.1 months for iDFS and 68.2 months for OS. The iDFS (1103 events [35.2%]) rates were 88.9% and 73.9% at 2 and 5 years. The OS (554 events [17.7%]) rates were 97.4% and 90.5% at 2 and 5 years. There was a significant and high correlation ( &amp;gt;0.85 based on IQWiG 2011 guidelines) between iDFS and OS in the overall cohort (Pearson 0.91, P&amp;lt; .001; Spearman 0.88, P&amp;lt; .001) with 82% of OS variation explained by iDFS (least square R2=0.82; Table). Results were confirmed by IMI rho (0.83, P&amp;lt; .001), which is interpreted as very strong ( &amp;gt;0.8). Results were consistent among all reported subgroups; Pearson and Spearman correlations exceeded 0.85 and IMI exceeded 0.8, except for pts with stage III disease where correlation remained high (Pearson 0.88, P&amp;lt; .001) or medium/strong (Spearman 0.84, P&amp;lt; .001; IMI 0.79, P&amp;lt; .001) and where most censoring was observed (38.2% of pts). Conclusions: This retrospective cohort analysis demonstrates a very strong pt-level surrogacy between iDFS and OS among pts with HR+/HER2− EBC treated in a real-world, US-based, academic and community setting. The findings complement the trial-level surrogacy from prior analyses using data from randomized controlled trials and support iDFS as a surrogate endpoint for OS in HR+/HER2− EBC trials. Citation Format: Stephanie Graff, Sara Tolaney, Lowell Hart, Pedram Razavi, Wolfgang Janni, Lee Schwartzberg, Andrii Danyliv, Juan Carlos Mora Payan, Ilia Ferrusi, Rishi Rajat Adhikary, Joyce O'Shaughnessy. Invasive disease-free survival as a surrogate for overall survival in patients with hormone receptor−positive/human epidermal growth factor receptor 2−negative early breast cancer: a real-world analysis [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 PO1-17-07.

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 GS03-07: Protocol-defined biomarker analysis in the PALLAS (AFT-05) adjuvant trial: Genomic subtype derived from RNA sequencing of HR+/HER2- early breast cancer

Abstract Background. The phase 3 PALLAS trial (NCT02513394) compared two years of the CDK4/6 inhibitor palbociclib with endocrine therapy of provider choice, versus endocrine therapy alone, as adjuvant treatment for patients with Stage II-III hormone receptor-positive HER2-negative (HR+/HER2-) breast cancer. Genomic subtype (PAM50 intrinsic subtype) measured from whole-transcriptome RNA sequencing data was defined in the protocol of the PALLAS trial as the primary biomarker for analysis of prediction and prognosis. Clinical data have been previously presented (Gnant et al, JCO 2022), and the trial now has 5-year median follow-up. Methods. As part of trial eligibility, all participants in PALLAS provided a tumor tissue block prior to randomization (surgical if primary resection, core biopsy if neoadjuvant treatment) for translational analyses (TRANS-PALLAS). The biorepository and laboratory were blinded to identity and processed samples in random order, to minimize bias. Nucleic acids were extracted from samples with sufficient tumor tissue and cellularity (&amp;gt;25 mm2 with ≥20% cancer nuclei). The Genome Sequencing Center at Washington University St. Louis performed whole-transcriptome RNA sequencing. Libraries were prepared from 1 µg DNase-1 treated total RNA, if total RNA DV200 &amp;gt;28 (Agilent Bioanalyzer), using an unbiased library protocol of RNA HyperPrep kit with RiboErase (HMR) (Kapa Biosystems, Wilmington, MA). 100 bp paired-end sequencing was performed on NovaSeq 6000 using S4 Reagent Kit (Illumina, San Diego, CA), with 48 libraries pooled per lane. Intrinsic subtype was determined using Bioclassifier package (Research PAM50 script, Parker et al.) only for the analysis population of primary breast cancer samples that had not been exposed to prior neoadjuvant therapy. Invasive disease-free survival (IDFS) will be visualized using Kaplan-Meier plots, with log-rank test between groups. Cox models of proportional hazards will be developed to evaluate prognosis adjusted for known clinical covariates, or for predictive interactions. The pre-defined level of significance is a two-sided 0.05. Results. From the total study population of 5796 enrolled patients, 4655 tissue blocks had sufficient tumor content to process for RNA, with 3931 yielding sufficient RNA for sequencing, and 2669/4655 (57.3%) submitted tissue blocks had DV200 ≥28 and were successfully sequenced. Clinical unblinding revealed 2370 unique patients (1182 in the palbociclib treatment arm and 1188 in the control arm) with intrinsic subtype defined from their untreated primary tumor: 1555 (65.6%) luminal A, 287 (12.1%) luminal B, 167 (7.0%) HER2-enriched, 310 (13.1%) basal-like, 51 (2.2%) normal-like. We will report the results for association of molecular subtype, proliferation score, and Risk of Recurrence (ROR) scores with invasive disease-free survival (IDFS) by treatment arm at the meeting. Conclusions. The TRANS-PALLAS cohort represents one of the largest biorepositories of HR+/HER2- early breast cancer reflecting contemporary systemic management in the framework of a prospectively randomized global trial. Required tumor block submission in this phase 3 trial yielded data from unbiased whole-transcriptome RNA sequencing of the primary tumor prior to treatment from 41% of the PALLAS participants. The proportion of luminal A cancers was unexpectedly high (66%), indicating a lower-risk distribution of cancers in this population. The planned analyses of prediction and prognosis are ongoing and those results will be presented at the time of the meeting. Support: AFT, ABCSG, Pfizer, ECOG-ACRIN, NSABP Foundation, GBG, BIG; Clinicaltrials.gov Identifier: NCT02513394; https://acknowledgments.alliancefound.org Citation Format: Daniel Stover, Dominik Hlauschek, Erica Mayer, W. Fraser Symmans, Mark Watson, Iros Barozzi, Martin Filipits, Karla Ballman, Meritxell Bellet- Ezquerra, Justin Balko, Gabor Rubovszky, Nicholas Zdenkowski, Adam Brufsky, Guenther Steger, Claudine Isaacs, Sibylle Loibl, Fernando Henao, Meredith Regan, Yuan Liu, Christian Fesl, Patrick O'Brien, Angela DeMichele, Michael Gnant, Otto Metzger. Protocol-defined biomarker analysis in the PALLAS (AFT-05) adjuvant trial: Genomic subtype derived from RNA sequencing of HR+/HER2- 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 GS03-07.

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 PO3-17-01: Brazilian Real-world data of HR+ HER2- early-stage Breast Cancer (BC) patients are poor when compared to control arms of recent adjuvant clinical trials

Abstract INTRODUCTION: In Brazil, BC is the most common neoplasm among women, with 73k new cases annually. Adjuvant hormone therapy (HT) options are evolving with personalized strategies based on risk stratification. Real-world data (RWD) plays a crucial role in understanding the outcomes in BC patients (pts) in low- and middle-income countries, where significant health disparities, access gaps, and barriers to the implementation of guidelines exist. This study aims to assess the epidemiologic profile, practice patterns, and real-world outcomes of pts with ER+ HER2- stage I-III BC treated in the largest network of private oncology services in Brazil and compare results with control arms of recent clinical trials evaluating CDK4/6 inhibitors in adjuvant setting. METHODS: Retrospective RWD study from Oncoclínicas Group with longitudinal EHR data from 2017 to 2022 merged in a platform where structured variables (demographics, tumor staging, pharmacy records) are integrated with unstructured data from physician notes and digitized pathology-molecular reports using technology-based abstraction performed by expert human curators that follow mCODE standards and predefined ontology. Treatment patterns and invasive disease-free survival (IDFS) outcomes were collected. Regarding risk stratification, pts were classified as high-risk (HR) if: (i) 4+ axillary lymph nodes (LN), or (ii) 1-3 LN and grade 3 and/or Ki620% and/or high-risk ODX/Mammaprint; intermediate-risk (IR) if: (iii) 1-3 LN with grade 1-2 and/or Ki67 &amp;lt; 20% and/or non-high-risk ODX/Mammaprint, or (iv) N0 with grade 2-3 and/or Ki67 &amp;gt;20% and/or high-risk ODX/Mammaprint; and low-risk (LR) if: (v) all other stages I and IIA not having the risk factors above. RESULTS: From over 30k BC pts in Oncoclínicas Database, 19k had HR+/HER2- early BC, 12k were treated in high-volume clinics, and 1,786 cases were selected for the study (diagnosis and first treatment in the last 6 years, complete histopathology and pharmacy registries). The median age was 57 years (27-96), 566 (32%) pts were premenopausal, 1052 (59%) had stage I disease, 372 (21%) stage IIA, 165 (9%) stage IIB and 197 (11%) stage III BC. Regarding risk stratification, 1,179 (66%) were LR, 351 (20%) IR, and 256 (14%) HR. In post-menopausal pts, aromatase inhibitor (AI) was used by 74% of pts with LR, 79% with IR and 83% with HR. In premenopausal pts, ovarian function suppression (OFS) – combined with tamoxifen or AI – was prescribed to 18% of LR pts, 15% of IR pts, and 48% of HR pts. Chemotherapy (CT) was offered to 32%, 38%, and 73% of postmenopausal pts in LR, IR, and HR groups. In premenopausal pts, 55%, 57%, and 78% received CT in LR, IR, and HR groups. The 3-year iDFS in the general population was 85%, reaching 80% in premenopausal and 86% in postmenopausal pts. The overall 3y iDFS was 87% in the LR, 86% in IR, and 72% in HR. Among premenopausal pts, the 3y iDFS was 81% in LR, 92% in IR, and 64% in the HR group. While the risk distribution of our cohort is similar to recent clinical trials, the 3y iDFS outcomes were numerically lower to those observed in the control groups of the pivotal trials evaluating adjuvant CDK4/6 inhibitors. In the HR group, the 3y iDFS was 72% (versus 84% 3y iDFS in the control arm of the MonarchE trial). Combining the IR/HR groups, the 3y iDFS was 80% (versus 87% in the control arm of NATALEE trial). CONCLUSION: In this large RWD cohort treated in a private setting in Brazil, most pts are diagnosed with stage I and LR BC. In this cohort, a significant proportion of premenopausal pts with IR/HR are not treated with OFS and do not receive CT. Real-world survival outcomes of Brazilian women with HR+ HER2- early BC treated in private clinic are inferior to those observed in recent clinical trials, especially in the premenopausal pts. In public healthcare system, where prevalence of HR disease is higher and access to essential treatments more limited, outcomes might even be worsened compared to the ones presented here. Citation Format: Aline Goncalves, Tomas Reinert, Max S. Mano, Heloisa Cruz, Cristiano Resende, Gustavo Bretas, Carlos Barrios, Matheus Costa e Silva, Rafael Paes, Guilherme Silva, Erika Martins, Fernanda Koyama, Bruno Ferrari, Carlos Gil Ferreira, Pedro Aguiar Junior, Rodrigo Dienstmann. Brazilian Real-world data of HR+ HER2- early-stage Breast Cancer (BC) patients are poor when compared to control arms of recent adjuvant clinical trials [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 PO3-17-01.

Abstract PO3-20-01: ASTEFANIA: a Phase III study of ado-trastuzumab emtansine plus atezolizumab or placebo as adjuvant therapy in patients with residual invasive breast cancer after neoadjuvant HER2-targeted therapy and chemotherapy

Abstract BACKGROUND Ado-trastuzumab emtansine (T-DM1) is the standard of care for adjuvant treatment of patients (pts) with HER2-positive early breast cancer (eBC) who have invasive residual disease after preoperative treatment with taxane and HER2-targeted therapy. However, a high unmet need remains in some higher risk subgroups (e.g., inoperable or lymph node-positive, hormone receptor-negative disease) who have 3-year invasive disease-free survival (IDFS) rates of 76%. Exploratory analyses suggest that addition of the programmed death-ligand 1 (PD-L1) inhibitor atezolizumab to T-DM1 results in longer progression-free survival compared with T-DM1 alone in pts with previously treated PD-L1-positive metastatic BC. PD-L1/programmed death-1 inhibitors may have a different effect in eBC, as they result in improved pathologic complete response in early triple-negative BC regardless of PD-L1 status. ASTEFANIA evaluates atezolizumab plus T-DM1 in PD-L1-unselected pts with higher risk residual invasive breast cancer after neoadjuvant treatment. TRIAL DESIGN ASTEFANIA is a Phase III, randomized, double-blind, multicenter, study in pts with centrally confirmed HER2-positive eBC with residual invasive disease at surgery after neoadjuvant chemotherapy and HER2-directed treatment including ≥9 weeks of taxane and ≥9 weeks of trastuzumab. Within 12 weeks of primary surgery, pts are randomized 1:1 to intravenous (IV) T-DM1 3.6 mg/kg every 3 weeks (q3w) plus atezolizumab 1200 mg IV q3w or T-DM1 3.6 mg/kg IV q3w plus placebo IV q3w for 14 cycles. Radiotherapy and/or endocrine therapy is administered per local standards. Randomization is stratified by clinical stage at presentation, hormone receptor status, preoperative HER2-directed therapy, and PD-L1 status. ELIGIBILITY CRITERIA Eligible pts have clinical stage cT4/any N/M0, any cT/N2–3/M0, or cT1–3/N0–1/M0 at presentation. Those with cT1–3/N0–1 disease must have pathologic evidence of residual invasive carcinoma in axillary lymph node(s) at surgery. Pts with cT1mi/T1a/T1b/N0 disease are not eligible. AIMS The primary endpoint is IDFS. Secondary endpoints include overall survival, safety, and patient-reported outcomes. STATISTICAL METHODS The log-rank test will be used to compare IDFS between the treatment arms, according to the protocol-defined stratification factors. The Cox proportional hazards model, stratified by the protocol-defined stratification factors, will be used to estimate the hazard ratio between the two treatment arms and its 95% confidence intervals. ACCRUAL As of Jun 28, 2023, 789 pts of the target of 1,700 have been enrolled. CONTACT INFORMATION For more information or to refer a patient, email global.rochegenentechtrials@roche.com or call 1-888-662-6728 (USA only). Clinicaltrials.gov number NCT04873362. Originally presented at the ESMO Congress 2021, 202TiP, Peter Schmid et al. – Reused with permission. Further information is available in Future Oncology 2022; 18:3563–3572. Submitted with permission from Future Medicine &amp; Future Science, part of the Future Science Group. Citation Format: Peter Schmid, Thomas Bachelot, Giampaolo Bianchini, Nadia Harbeck, Sherene Loi, Yeon Park, Aleix Prat, Leslie Gilham, Thomas Boulet, Nino Gochitashvili, Estefania Monturus, Chiara Lambertini, Beatrice Nyawira, Adam Knott, Sara Hurvitz. ASTEFANIA: a Phase III study of ado-trastuzumab emtansine plus atezolizumab or placebo as adjuvant therapy in patients with residual invasive breast cancer after neoadjuvant HER2-targeted therapy and chemotherapy [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 PO3-20-01.

Abstract PO3-08-03: Comparing prognosis for BRCA1, BRCA2 and non-BRCA breast cancer

Abstract BACKGROUND Breast Cancer (BC) is the most diagnosed malignancy and the leading cause of cancer death in women worldwide. Approximately 10% of BC cases are hereditary, and up to 25% have been linked to germline variants of specific genes. Germline pathogenic variants (PV) in BRCA1 and BRCA2 genes, which account for 20% of familial BC cases, are highly penetrant and are associated with Hereditary Breast/Ovarian Cancer Syndrome. BRCA1 e BRCA2 are tumor suppressor genes, which interact with recombination/DNA repair proteins in pathways that participate in preserving intact chromosome structure, particularly on the DNA double chain. So far, more than 7000 PV were identified on these genes, including the Portuguese founder mutation (BRCA2 c.156_157insAlu), which accounts for a great proportion of BC cases in our country. BRCA1 and BRCA2 associated BC have distinct clinicopathological characteristics. Long-term follow-up data related to prognosis and survival of either BRCA1 or BRCA2 BC patients is conflicting. Two large meta-analysis report worse overall survival for both, when compared to sporadic BC, whereas two other large meta-analysis concluded on worse overall survival only for BRCA1 patients, with similar overall survival for BRCA2 patients. One meta-analysis reports similar survival for both groups. We report the analysis of our cohort of BRCA1/2 BC patients included in our multidisciplinary program. Our goal is to compare clinicopathological characteristics and prognosis between BRCA1 and BRCA2 BC and with a control group without germline PV (non-BRCA). METHODS Prospective follow-up was proposed to patients with a diagnosed BRCA1/2 PV. This study included BRCA1/2 patients with BC as first cancer diagnosis, observed between January 2000-May 2023. A control group, with similar phenotype and histological characteristics, without germline PV was used. Statistical analysis was performed to compare characteristics and prognosis between BRCA1 and BRCA2 and non-BRCA BC. ANOVA test was used to compare the age at diagnosis; chi-square was used to compare categorical variables, such as histological subtype and clinical staging at diagnosis; log rank was used to compare the primary and secondary endpoints – overall survival (OS) and invasive disease-free survival (iDFS), respectively. RESULTS From 1077 individuals who tested positive for BRCA1/2 PV, 345 patients had BC, mostly with a BRCA2 PV (66.4%). A control group of 339 individuals was assembled. BRCA2 BC was mostly luminal, as non-BRCA patients, compared with BRCA1 (73.8% vs. 65.8% vs. 25.9%, p&amp;lt; 0.001) and BRCA1 was mostly triple negative, compared with non-BRCA and BRCA2 (65.5% vs. 16.5% vs. 13.3%, p&amp;lt; 0.001). For a mean follow-up time of 10.6 years (±5.6), recurrence was similar, with central nervous system (CNS) metastases being more frequent for BRCA1 (66.7% vs. 23.7% in non-BRCA, and vs. 9.1% in BRCA2, p&amp;lt; 0.001), and bone metastases were predominant for BRCA2 BC (57.5% vs 33.3% in non-BRCA, and vs. 9.1% in BRCA1, p=0.003). Non-BRCA BC showed longer time to recurrence (99.3 months vs. 76.5 months in BRCA2 BC, and vs. 61.2 months in BRCA1 BC, p=0.010), although longer OS was observed in BRCA2 BC (136.2 months vs. 121.7 months in BRCA1 BC, and vs. 113.2 months in non-BRCA, p&amp;lt; 0.001). Development of second primary tumors was more frequent in BRCA2 patients, compared with BRCA1 (20.9% vs 9.2%, p=0.002). DISCUSSION In the Portuguese population, BRCA2 BC is more frequent than BRCA1 BC. Relapses occurred later for BRCA2 BC, affecting mostly the bone, whereas BRCA1 BC relapsed in CNS. As it is stated in the literature, BRCA1 BC is consistent with triple negative, as BRCA2 BC is more associated with luminal subtype. Differences in iDFS favored non-BRCA patients, whereas OS was significantly improved in BRCA2 BC patients. This is the biggest cohort presented in the Portuguese population and one of the biggest presenting BRCA2 BC patients. Table 1 Characteristics of patients according to BRCA1/2 mutation status (n = 684) Citation Format: Pedro Antunes Meireles, Catarina Bexiga, Sofia Fragoso, Sidónia Santos, Teresa Duarte, Fátima Vaz. Comparing prognosis for BRCA1, BRCA2 and non-BRCA 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 PO3-08-03.

Abstract PO5-19-01: The HER2-RADiCAL study (Response ADaptive CAre pLan) – Tailoring treatment for HER2 positive early breast cancer

Abstract Background The presence or absence of residual disease following neoadjuvant systemic anti-cancer therapy (neoSACT) for HER2-positive early breast cancer (HER2+ EBC) provides powerful prognostic information. Pathological complete response (pCR) following neoSACT, particularly in patients with earlier clinical TNM stage at diagnosis, identifies a population with excellent survival outcomes in whom the balance of toxicity associated with the current treatment pathway may be disproportionate to absolute clinical benefit. Aims &amp;gt;HER2-RADiCAL seeks to reduce the treatment burden and healthcare costs of treating HER2+ EBC by testing the hypothesis that pCR can be used as a functional response biomarker to select patients who can safely receive less systemic therapy with minimal/no loss of efficacy. Trial design and eligibility criteria HER2-RADiCAL is a response-directed interventional cohort/threshold-crossing design study embedded within a real-world data-driven clinical pathway model. Patients with ER-positive or negative HER2+ EBC with cT1N1 or cT2N0-1 stage at diagnosis are eligible after completion of standard of care neoSACT and locally determined pCR (ypT0/Tis ypN0). Patients with pathological features consistent with previous malignant involvement in &amp;gt;4 nodes are not eligible. Adjuvant trastuzumab +/- pertuzumab may have continued prior to study entry provided no more than 9 cycles of trastuzumab are received. After registration all participants receive a total of 9 cycles of trastuzumab including those administered prior to study entry. Participants receive no further pertuzumab and no adjuvant chemotherapy. Adjuvant endocrine therapy and radiotherapy are given as per standard of care. Central pathology review of pCR status will be conducted in a subset of cases. A Study Within a Trial (SWAT) will explore identification of factors influencing patient decision-making for participation in studies of response-adapted treatment. Statistical methods The primary endpoint is relapse-free interval. Recruitment of 720 participants over 3.5 years will provide 90% power to exclude an event rate &amp;gt;6.5% at 3 years (expected event rate ≤4%). Secondary endpoints include relapse-free survival, invasive breast cancer-free survival, invasive disease-free survival, distant recurrence-free interval, breast cancer-free interval, overall survival, treatment pathway adherence and cost-effectiveness. An interventional cohort is preferred to a randomised non-inferiority trial based on the known event rate in this population which is sufficiently low such that any deviation from this expected event rate would indicate failure of the reduced therapy strategy. Real-world data driven clinical pathway model Health economic modelling will compare the protocol-driven study cohort with two comparator pathways: a non-response adapted maximum therapy pathway (the standard clinical pathway prior to the study) and a real-world representative pathway derived from anonymised data for all patients treated for HER2+ EBC within the UK NHS. Patient and public involvement Our PPI partners continue to shape this research, holding key roles as trial management group members, overseeing progress of the study, contributing to protocol amendment development, and design and implementation of the SWAT. Current status The first patient was enrolled in December 2021. At 10th July 2023, 25 research sites have opened with 39 participants recruited. Site opening continues with a minimum target of 40. Responding to continued use of anthracycline-based regimens in UK practice, eligibility criteria have recently been extended to permit entry of patients who have received anthracycline-containing neoSACT. For further information contact her2radical-icrctsu@icr.ac.uk. Citation Format: Iain Macpherson, Stuart McIntosh, Lucy Kilburn, Holly Tovey, Laura Moretti, Katie Goddard, Indrani Bhattacharya, Clinton Boyd, Cliona Kirwan, Ciara O'Brien, Duncan Wheatley, Jennifer Glendenning, Mairead MacKenzie, Hilary Stobart, Claire Snowdon, Andrew Wardley, Abeer Shaaban, Peter Hall, David Cameron, Judith Bliss. The HER2-RADiCAL study (Response ADaptive CAre pLan) – Tailoring treatment for HER2 positive 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 PO5-19-01.