MINDACT Trial Research Articles

Characterizing the 70-gene MammaPrint risk stratification in Chinese luminal type breast cancer and its correlation with clinicopathological characteristics, immune and metabolic functions.

e12559 Background: The 70-gene MammaPrint is endorsed by the NCCN guidelines for predicting 5-year distant metastasis risk in HR+, HER2-, with 0-3 lymph nodes, early invasive breast cancer. Similarly, it is recommended by the CSCO breast cancer guidelines for prognostic assessment post breast cancer surgery. However, no prior studies have investigated its application in Chinese luminal-type breast patients or its correlation with immune and metabolic functions. Methods: This analysis encompasses 76 early-stage invasive Luminal breast cancer patients, registered at the First People's Hospital of Foshan between 2020 and 2023, with recorded clinical characteristics under informed consent. Patient-reported data include clinical features, pathology, and the 70-gene MammaPrint risk of recurrence. Additionally, RNA-seq analysis was conducted in 24 patients. Results: Among 76 enrolled patients,55.3% were categorized as MammaPrint low risk (MP-Low), and 44.7% as MammaPrint high risk (MP-High). Patients over 50 were more likely MP-Low (p=0.028, OR=2.860), while those with >20% Ki67-stained cells were prone to MP-High (p<0.001, OR=0.160). Comparing with MINDACT, there was 52.3% consistency, with 55.6% of MP-Low patients being C-Low (MINDACT risk Low) and 47.1% of MP-High patients being C-High (MINDACT risk High). Notably,21% of C-Low patients showed MP-High risk, and 27% of C-High patients exhibited MP-Low risk, of which 83.3% were ≥50 years old. Based on MINDACT and ISPY2 trial outcomes, patients were further categorized into four groups: MP-Ultralow, MP-Low but not ultralow (LNUL), MP-High but not ultrahigh (HNUH) and MP-Ultrahigh. The study identified an 18% MP-Ultralow population, suggesting that excessive adjuvant therapy might be avoided in these patients. Additionally, 41% of patients were identified as LNUL group, indicating potential benefit from adjuvant treatment or endocrine prolongation therapy. 4% were identified as MP-Ultrahigh group, suggesting potential benefits from neoadjuvant targeted therapy, albeit a poorer long-term benefit in the non-pCR portion. Further transcriptome analysis in 24 patients revealed significantly higher levels of Th2 cells in the MP-High group, with no significant difference observed in CD8 T cells between the two groups. Meanwhile, metabolic-related signatures also differed, with significantly higher levels of Dopamine, Norepinephrine, Heme, and Epinephrine biosynthesis in the MP-Low group. Conclusions: This study elucidates the intricate relationships between MammaPrint prediction results of 70 genes and clinical characteristics, immune and metabolic signatures in Chinese Luminal type breast cancer patients. The refined risk classification provides valuable insights for precision treatment, advancing personalized therapeutic strategies.

Association of MammaPrint index and 3-year outcome of patients with HR+HER2- early-stage breast cancer treated with chemotherapy with or without anthracycline.

511 Background: The MammaPrint (MP) risk of distant recurrence signature identifies hormone receptor-positive (HR+), HER2-negative early-stage breast cancer (EBC) patients (pts) with increased or decreased chemosensitivity and chemotherapy (CT) benefit. The MINDACT trial demonstrated excellent outcomes for MP Low Risk tumors without CT, and previous studies show MP High Risk tumors exhibit higher sensitivity and benefit with CT. There remains an unmet clinical need for identifying biomarkers to inform specific regimen planning for pts who qualify for CT. Here, the association of MP index and 3-year (yr) Recurrence-Free Interval (RFI) was evaluated in pts with HR+HER2-, genomically High Risk Luminal B-Type EBC treated with taxane and cyclophosphamide (TC) vs anthracycline + TC (AC-T). Methods: The prospective, observational FLEX Study (NCT03053193) includes stage I-III breast cancer pts who received MP testing, with or without BluePrint (BP) molecular subtyping, and consented to full transcriptome and clinical data collection. Pts with HR+HER2- MP High Risk and BP Luminal B-Type tumors who received chemotherapy with 3-yr follow-up data (N = 614) were included. High Risk tumors were further classified into High 1 (H1; 0.000 to -0.569) or High 2 (H2; -0.570 to -1.000). Differences in 3-year RFI, defined as time from diagnosis to a local-regional recurrence, distant recurrence, or breast cancer specific death per STEEP 2.0 criteria, between H1 and H2 tumors were evaluated by Kaplan-Meier analysis and log-rank test, stratified by CT regimen. Results: Patients had similar age, menopausal status, race, and lymph node status between H2 vs H1 tumors. H2 tumors were more likely Grade 3, compared to H1 tumors. 86% of tumors were classified as H1 Luminal B-Type (N = 530) and 14% were classified as H2 Luminal B-Type (N = 84). AC-T treated tumors had non-significant differences in 3-yr RFI between H1 Luminal B-Type (95.3% [95% CI, 91.8-98.8]; N = 184) and H2 Luminal B-Type (97.7% [95% CI, 93.4-100.0]; N = 44). In contrast, pts with H2 Luminal B-Type (N = 40) tumors treated with TC demonstrated a significantly worse RFI of 86.4% (95% CI, 74.2-100.0) compared with 97.1% (95% CI, 95.1-99.2) in pts with H1 Luminal B-Type (N = 346) tumors, with an absolute difference of 10.7% (p = 0.0076). Conclusions: These data show that among pts with Luminal B-Type tumors, MP H2 have significantly worse 3-yr RFI than pts with MP H1 tumors when treated with TC. This further supports ongoing research demonstrating the significant benefits of anthracycline-based CT for treating H2 Luminal B-Type tumors. Conversely, MP H1 tumors do not appear to benefit from the addition of anthracycline to CT regimen. These FLEX data add to the growing evidence identifying MammaPrint as a comprehensive genomic signature regarding both prognosis as well as selection of systemic therapy for HR+HER2- EBC pts. Clinical trial information: NCT03053193 .

Abstract PO5-01-14: Genomic risk analyses in patients with clinical low risk ER-positive HER2-negative early breast cancer developing an early metastatic event

Abstract Background: Over the past decade, there have been notable changes in the definition of risk estimation in patients with early-stage breast cancer (EBC). Specifically, within the timeframe of 2000 to 2017, following Estrogen Receptor (ER) positive and HER2-negative EBC cases were classified as low risk according to the University Hospitals of Leuven (UHL) criteria of that time: if ER H-score was >200: all patients with tumors N0 and Grade (G) 1, ≤pT2; or G2-3 pT1a-b; in patients ≥40 years with tumors N0 and G2 pT1c-2 or G3 pT1c; in patients ≥ 55 years with tumors N0 G3 pT2 or N1 any Grade, pT≤2. For lower H-scores, other criteria applied. However, despite undergoing endocrine therapy, a subset of these patients with clinically low-risk tumors unexpectedly experienced metastasis within five years of initial diagnosis. This unforeseen outcome may indicate potential undertreatment, as these patients did not receive adjuvant chemotherapy. We have conducted a case-cohort study of those patients with early relapse and performed the current clinical risk assessment methods and genomic risk analyses. Methods: In this study, we included patients with ER-pos, HER2-neg early-stage breast cancer diagnosed between 1-1-2000 and 31-12-2017, who were classified as low-risk tumors by UHL guidelines at that time, who were older than 35 but younger than 71 years, had an unilateral, unifocal breast tumor with tumor size up to 5 cm. These patients did not receive adjuvant chemotherapy. We selected the patients that experienced early distant recurrence, defined as distant recurrence (DR) within 5 years after the initial diagnosis. To ensure comparability for the analyses they were matched to controls for grade, menopausal status, tumor size, lymphovascular invasion, progesterone receptor status, and the year of diagnosis. For each patient, we have calculated the clinical risk score according to the criteria outlined by Mymammaprint.com, based on the modified Adjuvant Online tool used in the MINDACT trial. For the analysis, formalin-fixed paraffin-embedded (FFPE) breast tumor tissue samples were subjected to in-house validated targeted RNA-based Mammaprint(MP) analysis by NGS (MP Agendia). Results: Of the 3190 patients with EBC at UHL during the study period, 2476 patients were considered for this analysis and fitted the clinical low-risk criteria defined low-risk at UHL. Among those, only 42 or 1.7% of the eligible cohort had developed metastasis within 5 years. Tissue for MP analysis was available for 35 of these cases and for their matched control. Due to technical failure, the 1:1 matching was lost and MP results were known for 28 cases and 27 controls. The patient and tumor characteristics of both groups were comparable. In this UHL clinical low-risk group, 21/28 (75%) cases would be identified as clinical high-risk by MyMammaprint.com and 18/27 (67%) controls. We identified 13 patients (46.43%) with high genomic risk within the group with DR and 9 (33.33%) within the control group. There was no statistically significant difference (p=0.412) in the proportion of genomically high-risk patients within the group with DR compared to the control group. Conclusions: In a database of patients with EBC of whom 98% did not develop metastasis within 5 years, we observed in a small series of chemotherapy naïve patients with early DR and UHL-defined clinical low-risk tumors, that nearly half had a genomically high risk of distant metastasis. Albeit numerically higher than the matched-control group, this observation was not significant and would warrant a larger sample size and power to confirm these results. Table. Genomic versus Clinical Risk by MyMammaprint.com Citation Format: Josephine Van Cauwenberge, Hava Izci, Hans Wildiers, Sileny Han, Christine Desmedt, Giuseppe Floris, Sara Vander Borght, Ann Smeets, Ines Nevelsteen, Isabelle Vanden Bempt, Patrick Neven. Genomic risk analyses in patients with clinical low risk ER-positive HER2-negative early breast cancer developing an early metastatic event [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 PO5-01-14.

Abstract PO1-02-05: An exploratory comparison of MINDACT and TAILORx genomic risk proportions and outcomes in patients with HR+/HER2-, node-negative early-stage breast cancer, stratified by clinical risk

Abstract Introduction: Genomic tests provide physicians with critical information to evaluate the risk of distant metastasis and inform treatment plans by identifying those patients who may safely avoid chemotherapy (CT). The 70-gene signature (MammaPrint, MP) through the MINDACT trial and the 21-gene signature (Oncotype DX, ODx) through the TAILORx trial are the only tests validated with level 1A evidence that can be used for CT de-escalation decisions. Differences in trial design have made direct comparison of results difficult. We provide a comparison of MammaPrint and ODx genomic risk distributions and associated survival in patients with HR+/HER2-, node-negative (N0) early-stage breast cancer (EBC), stratified by clinical risk. Methods: Data from the MINDACT 2021 publication in The Lancet Oncology and landmark TAILORx 2019 publication in The New England Journal of Medicine were reviewed, in addition to publicly available data submitted to the Dutch Health Technology Assessment (HTA) authorities regarding survival data in patients with clinical High Risk in TAILORx. In MINDACT, patients were randomized based on both clinical (as per MINDACT definition) and genomic risk (clinical high/MP low, randomized to treatment according to clinical risk [i.e. CT] vs treatment according to MammaPrint risk [i.e. no CT]), while in TAILORx randomization was based on genomic risk alone. In TAILORx, enrollment for the population in the RS 11–25 group was enriched by 73% to account for the larger than expected non-adherence to randomized treatment plan based on the ODx results, as described in the original publication. This enrichment was only done for the RS 11–25 group. In this analysis, this enrollment enrichment was removed by applying the same proportional 73% corrective factor to the RS 11–25 group. Outcome data are reported for Overall Survival (OS), the only comparable endpoint used in both trials. Results: This explorative comparison focuses on patients with HR+/HER2- and N0 EBC in MINDACT (n=4,225) and TAILORx (n=6,686, without population enrichment). Similar proportions of patients identified as candidates for CT de-escalation (MP Low Risk or ODx RS≤25) were observed in this population of MINDACT (75%) and TAILORx (80%) when removing the RS 11–25 population enrichment in TAILORx (Table). In clinical high risk patients, the proportion with genomic low risk of distant metastasis were also comparable between MINDACT (55%) and TAILORx (63%) (Table). In the original clinical high risk but MammaPrint Low Risk population treated without CT in MINDACT the reported 8-year OS was 93.9%. In TAILORx, the comparable population of patients (ie. clinical high risk, low genomic risk, not treated with CT) had a 9-year OS of 89.2% in the RS 0–10 group and 91.6% in the RS 11–25 group (Table). Conclusions: Accounting for differences in trial design and population, comparable proportions of patients with genomic low risk results were observed between MP and ODx, justifying similar rates of CT de-escalation. Patients with clinical high risk tumors who are MammaPrint Low Risk had an excellent survival at 8 years. Genomic risk distributions and associated OS in HR+HER2- N0 patients in MINDACT and TAILORx MP, MammaPrint; OS, Overall Survival; RS, Recurrence Score. Number of patients in the TAILORx RS 11 – 25 group are adjusted to remove the proportional enrichment in the trial. OS data presented per original MINDACT and TAILORx populations. Citation Format: Patrick Neven, Josephine Lopes-Cardozo, Fatima Cardoso, Laura Van ’t Veer. An exploratory comparison of MINDACT and TAILORx genomic risk proportions and outcomes in patients with HR+/HER2-, node-negative early-stage breast cancer, stratified by clinical risk [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 PO1-02-05.

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.

Locoregional Breast Cancer Recurrence in the European Organisation for Research and Treatment of Cancer 10041/BIG 03-04 MINDACT Trial: Analysis of Risk Factors Including the 70-Gene Signature.

A number of studies are currently investigating de-escalation of radiation therapy in patients with a low risk of in-breast relapses on the basis of clinicopathologic factors and molecular tests. We evaluated whether 70-gene risk score is associated with risk of locoregional recurrence (LRR) and estimated 8-year cumulative incidences for LRR in patients with early-stage breast cancer treated with breast conservation. In this exploratory substudy of European Organisation for Research and Treatment of Cancer 10041/BIG 03-04 MINDACT trial, we evaluated women with a known clinical and genomic 70-gene risk score test result and who had breast-conserving surgery (BCS). The primary end point was LRR at 8 years, estimated by cumulative incidences. Distant metastasis and death were considered competing risks. Among 6,693 enrolled patients, 5,470 (81.7%) underwent BCS, of whom 98% received radiotherapy. At 8-year follow-up, 189 patients experienced a LRR, resulting in an 8-year cumulative incidence of 3.2% (95% CI, 2.7 to 3.7). In patients with a low-risk 70-gene signature, the 8-year LRR incidence was 2.7% (95% CI, 2.1 to 3.3). In univariable analysis, adjusted for chemotherapy, five of 12 variables were associated with LRR, including the 70-gene signature. In multivariable modeling, adjuvant endocrine therapy and to a lesser extent tumor size and grade remained significantly associated with LRR. This exploratory analysis of the MINDACT trial estimated an 8-year low LRR rate of 3.2% after BCS. The 70-gene signature was not independently predictive of LRR perhaps because of the low number of events observed and currently cannot be used in clinical decision making regarding LRR. The overall low number of events does provide an opportunity to design trials toward de-escalation of local therapy.

Agreement on risk assessment and chemotherapy recommendations among breast cancer specialists: A survey within the MINDACT cohort.

Tailored recommendation for adjuvant chemotherapy in breast cancer patients is of great importance. This survey assessed agreement among oncologists on risk assessment and chemotherapy recommendation, the impact of adding the 70-gene signature to clinical-pathological characteristics, and changes over time. A survey consisting of 37 discordant patient cases from the MINDACT trial (T1-3N0-1M0) was sent to European breast cancer specialists for assessment of risk (high or low) and chemotherapy administration (yes or no). In 2015 the survey was sent twice (survey 1 and 2), several weeks apart, and in 2021 a third time (survey 3). Only the second and third surveys included the 70-gene signature result. 41 breast cancer specialists participated in all three surveys. Overall agreement between respondents decreased slightly between survey 1 and 2, but increased again in survey 3. Over time there was an increase in agreement with the 70-gene signature result on risk assessment, 23% in survey 2 versus 1 and 11% in survey 3 versus 2. With information available indicating a low risk 70-gene signature (n=25 cases), 20% of risk assessments changed from high to low and 19% of recommendations changed from yes to no chemotherapy in survey 2 versus 1, further increasing with 18% and 21%, respectively, in survey 3 versus 2. There is a variability in risk assessment of early breast cancer patients among breast cancer specialists. The 70-gene signature provided valuable information, resulting in fewer patients being assessed as high risk and fewer recommendations for chemotherapy, increasing over time.

Reflex MammaPrint testing on breast core biopsies: A single center experience.

e12581 Background: Breast cancer genomic assays are well established in the adjuvant setting, but still evolving in the neoadjuvant setting. Recent data shows that MammaPrint (MP)/BluePrint (BP) genomic assays in the neoadjuvant setting can reclassify hormone receptor positive (HR+), HER2 negative (HER2-) tumors into intrinsic phenotypes with corresponding responses to neoadjuvant therapy (NAC). We performed reflex MP/BP assays on invasive breast cancer core biopsies and evaluated the relationships between clinical risk, molecular risk and intrinsic phenotype. Methods: 150 consecutive HR+, HER2- invasive breast cancers were identified by core biopsy in a tertiary care cancer center and underwent reflex MP/BP testing by an external central laboratory between July 2021 and Jan 2022. Retrospective review was completed on patient demographics and tumor characteristics; descriptive statistics were performed. Results: Of 150 newly diagnosed HR+ HER2- breast cancers, 141 successfully had a reflex MP/BP test performed; 9 were not performed due to technical feasibility or clerical error. Of the 141 patients with a completed MP/BP assay, 7 had recurrent disease, and 8 had metastatic disease, these were excluded. Patients were categorized as clinically high (cHR) or low risk (cLR) using the criteria from the MINDACT trial and as molecularly high risk (MP HR) or low risk (MP LR) per their MP results. We then grouped patients with discordant clinical and molecular risk. We then examined clinical features and NAC receipt amongst these clinical and molecular risk groups. Conclusions: There was discordance between clinical and molecular risk in 38% of our cohort, 20% were cLR/MP and 18% were cHR/MP LR. The decision to give NAC was primarily driven by clinical risk as only 1 patient with cLR/MP HR received NAC. Amongst cHR/MP LR 87% did not get NAC, but this appears to have been a clinical decision as only 7 of these patients had a pre-operative oncology visit at which MP/BP was mentioned. Most (72%) of > cN1 patients received NAC, of the 5 who didn’t, 4 were in the MP LR group and had a pre-operative oncology visit where MP was mentioned. In this select group the genomic assay may have influenced the decision to withhold NAC. Reflex genomic assays for HR+ HER2- breast cancer may not be useful; the decision to integrate molecular risk into the decision for NAC is multifactorial and stage of disease may be most impactful. Further work is needed in this area. [Table: see text] [Table: see text]

115P Longterm prognostic utility of 70-gene signature by clinical and genomic risks, including Ultralow (gUL) risk patients (pts)

In the MINDACT trial, 4 risk categories (RC) by clinical (c) and genomic (g) risks were defined. In cHigh/gLow risk patients (pts) with no adjuvant chemotherapy (CT), 8y-Distant Metastases Free Survival (DMFS) was 89.4 % [95% CI 86.2-91.5]. MP also identified a third subgroup of gUL pts (score 0.355 – 1.0, 15% in MINDACT), with an excellent prognosis and no benefit from extended endocrine therapy (EET). We aimed to study: DFS/ DMFS by the 6 RC resulting from combining the 2 (c) categories with the 3 (g) groups; the timing of recurrences; and the putative benefit of EET for each genomic group. All ER+/HER2- BC pts with MP data diagnosed between 2012-2017 at Vall d'Hebron University Hospital were selected. cLow risk was defined as in MINDACT trial. To study the benefit of EET, a landmark analysis at 5y from ET initiation was conducted. 140 pts were identified. Baseline features: 47.8% premenopausal; stage I/II: 74%/26%; histological grade 1/2/3: 19.6%/74.9%/6.5%. cLow/cHigh: 67%/33%; gUL/gLow-Non-Ultralow (LNUL)/gHigh: 11.4%/53.6%/35%. PgR and Ki67 tended to correlate with MP g risks, but only the IHC-subtype reached statistically significance. Systemic adjuvant treatments [N/%]: ET 138/98.5%; ovarian function suppression for premenopausal pts 23/35%; CT: 45/32%; EET: 49/35.8%. After 8y-median FU, 15 DFS events and 11 DMFS were observed. DMFS in cHigh/gLow (UL+LNUL) without CT was 90.6% [81.1%; 100%]. DFS/DMFS rates by each c/g category are depicted in the table. Only 4 DMFS events occurred after 5 years, precluding to explore EET role by RCTable: 115PcLow-gULcLow-gLNULcLow-gHighcHigh-gULcHigh-gLNULcHigh-gHighN (%)13 (9.4)45 (32)35 (25)3 (2.2)30 (22)13 (9.4)8y-DFS (%)1009184.81009076.9CI 95%-83.2-99.871.6-100-79.9-10057.1-1008y-DMFS (%)10095.589.11009084.6CI 95%-89.6-10077.7-100-79.9-10067.1-1008y-DMFS (%)cHigh-gLow (UL+LNUL) No CT90.6% (CI 95% 81.1-100)8y-DMFS (%) in Mindact TrialcHigh-gLow (UL+LNUL) No CT89.4% (CI 95% 86.2-91.5) Open table in a new tab . In our series, DMFS rate in cHigh-gLow pts without CT was similar to that reported in MINDACT trial. In line with prior reports, gUL pts had excellent survival, while cHigh-gHigh group showed significantly poorer outcome. Albeit limited by small sample size, classification in 6 RCs instead of 4 seems useful to redefine prognosis. Additional FU is warranted to determine the EET benefit in each RC.

63P Ki67 values and MammaPrint (MP) genomic risk in early breast cancer: Correlation by ductal vs lobular histology

In MINDACT trial, 4 risk categories (RC) by clinical (c) and genomic (g) breast cancer (BC) risk were defined. The study showed that the cHigh/gLow group without chemotherapy (CT) had a 94.8 % (CI 95% 92.9-96-2) 5-year Distant Metastases Free Survival (DMFS), so meeting the trial primary objective. Recently, a MP g group with excellent prognosis, named ultralow (gUL), has been described (15% in MINDACT). However, few data exist regarding the distribution of these 4 MINDACT RC and the proportion of gUL in the invasive lobular carcinoma (ILC) population. Moreover, association of Ki67 values and MP RC is rarely studied, both in general population and, particulary, in ILC pts. We aimed to address all these questions by comparing our series of invasive carcinoma of non-special type (NST) and ILC pts in whom MP was performed. Pts with ER+/PgR±/HER2- early BC diagnosed from 2012 to 2020 in our institution and with MP data were reviewed. Clinical risk was defined as in the MINDACT trial; genomic risk defined by MP score (UL score: 0.355 to 1.00). 152 pts were identified. NST: 85%, ILC: 15%. Median age NST/ICL: 54/59 years. Histological grade (HG) 1/2/3 (NST vs ILC) 19%/73%/8% and 18%/82%/0%, respectively. UL (g) risk: 17 (13.2%) in NST, 3 (13%) in ILC. The distribution of RC is summarized in the table [UL and Low-non-Ultralow (LNUL) combined for small numbers in ILC]. Median Ki67 value by (g) RC (gLow vs High) in the NST group were 12 and 20: (p<0.001). Of note, in ILC pts median Ki67 was 15 for both MP (g) RC (p=0.77). Table: 63POverall (n=151)NST (n=129)CLI (n=22)cLow-gLow (N/%)61 (40.4)51 (39.5)10 (45.5)cLow-gHigh (N/%)39 (25.8)36 (27.9)3 (13.6)cHigh-gLow (N/%)36 (23.8)28 (21.7)8 (36.3)cHigh-gHigh (N/%)15 (9.9)14 (10.8%)1 (4.5) Open table in a new tab Our results suggest a trend for lower genomic RC in ILC population compared to NST pts. As expected, median Ki67 values correlated with MP genomic categories in overall population and in NST but, intriguingly, not in ILC pts. The small number of pts in this latter group limits results. Further data in wider populations are needed to establish the true association of Ki67 with MP categories in ILC population.

Abstract P5-14-01: Transcriptomic insights into lobular breast cancer biology: a retrospective analysis of the MINDACT clinical trial

Abstract Background: Invasive lobular carcinoma (ILC) represents the second most common subtype of breast cancer after invasive breast cancer of no special type (NST). In this retrospective analysis of the MINDACT trial, we aimed at identifying/refining the transcriptomic differences between: 1) estrogen receptor positive/HER2-negative (ER+/HER2-) ILC versus ER+/HER2- NST, 2) classic and non-classic ER+/HER2- ILC, and, 3) recurring and non-recurring ER+/HER2- ILC in the subgroup of patients with a low clinical and low genomic (cL/gL) risk (as defined by a modified version of Adjuvant Online! and the 70-gene signature). Patients and methods: Central pathology review was performed for histological subtype, grade and Ki67 (G.V.) for 5929/6693 (88.6%) of the patients included in the MINDACT trial (NCT00433589). Analysis of transcriptomic data adjusted for age and grade was performed using the R/Bioconductor package ‘limma’ to identify differentially expressed genes (DEGs). DEGs having absolute log-fold change (logFC)≥ 0.2 and FDR-adjusted p-value (q-value) &amp;lt; 0.05 were considered. Gene set enrichment analyses (GSEA) of MSigDB hallmark gene sets were performed. Adjusted Cox regression models were used to evaluate the association of these hallmarks with disease free survival (DFS) and distant recurrence free survival (DRFS). Results: After central pathological review, 464 patients with ER+/HER2- ILC and 3798 patients with ER+/HER2- NST were identified. Patients with ILC were significantly older at diagnosis, had larger tumors, less axillary nodal involvement, more grade 2 tumors than patients with NST. At the transcriptomic level, we observed a high number of DEGs between these 2 subgroups, confirming their distinct phenotype. CDH1, the gene coding for E-cadherin, was as expected the most highly overexpressed gene in NST versus ILC. We further observed an increased expression of leptin (LEP), leptin receptor (LEPR), lipoprotein lipase (LPL), and the fatty acid transporter CD36 in ILC. This could suggest that ILC relied on increased lipid uptake thanks to the increased contact of ILC tumor cells with the adipocytes. IGF1 was also overexpressed in ILC versus NST, as a potential consequence of high LEP and high LEPR expression. Differences were also evident with regard to the extracellular matrix (ECM), with many collagens, matrix metalloproteinases (MMPs) and other key enzymes (e.g. LOXL1) being differentially expressed. We confirmed a decreased ER-signaling and increased PI3K/Akt signaling in ILC versus NST. Out of the 464 ER+/HER2- ILC tumors, 253 (55%) were classic ILC and 211 (45%) non-classic ILC. There were more grade 3 tumors, more highly proliferative tumors and more nodal involvement in patients with non-classic versus classic ILC. At the transcriptomic level, differences were subtler than the differences seen above. Still, a significant enrichment of the hallmarks related to cell cycle in the non-classic ILC, and of the hallmarks related to epithelial-to-mesenchymal transition, hypoxia, adipogenesis and IL6/JAK/STAT3 signaling in classic ILC was observed. Finally, 216/464 patients with ER+/HER2- ILC (47%) were assigned to the cL/gL risk group and did not receive chemotherapy. 28/216 of these patients (13%) relapsed (DFS, median FU: 8.7 years). Enrichment of hallmarks related to apoptosis, inflammatory response, hypoxia and oncogenic signaling (PI3K/Akt, Ras, c-Myc) was associated with worse survival. Conclusion: This represents, to the best of our knowledge, the largest set of gene expression data for patients with ILC, issued from a clinical trial where histology was reviewed centrally. These results could be used to personalize treatment for patients with ILC. This project is funded by the Breast Cancer Research Foundation. Citation Format: Christine Desmedt, Ha-Linh Nguyen, François Richard, Sabine Linn, Otto Metzger, Coralie Poncet, Jelle Wesseling, Florentine Hilbers, Kim Aalders, Mauro Delorenzi, Suzette Delaloge, Jean-Yves Pierga, Etienne Brain, Suzan Vrijaldenhoven, Peter A Neijenhuis, Karen Van Baelen, Marion Maetens, Emiel Rutgers, Martine Piccart, Laura Van ’t Veer, Giuseppe Viale, Fatima Cardoso. Transcriptomic insights into lobular breast cancer biology: a retrospective analysis of the MINDACT clinical trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-14-01.

Abstract PD4-06: PD4-06 Obesity-associated changes in transcriptomic profile and immune landscape of primary breast cancer revealed by bulk and single-cell gene expression data

Abstract Background: Breast cancer (BC) is one of the cancer types recognized as an obesity-associated disease. Current understandings of molecular mechanisms underlying the BC-obesity connection however largely came from experimental models while systematic investigation of the impact of obesity on BC biology in large patient series is still lacking. The purpose of this study is to discover changes in the transcriptomic profile of primary BC according to patients’ body mass index (BMI). Data and Methods: Bulk and single-cell gene expression data from treatment-naïve primary breast tumors from non-underweight patients were retrieved from the MINDACT trial (NCT00433589; N = 1481) and the pre-treatment cohort of the BioKey trial (NCT03197389, N = 36), respectively. Three categories were considered for BMI: lean, overweight and obese. The main analyses focused on the invasive carcinoma of no special type (NST) estrogen receptor-positive/HER2-negative (ER+/HER2-, N_bulk = 735, N_single-cell(sc) = 10) and NST ER-/HER2- (N_bulk = 118, N_sc = 15) subgroups. The bulk expression data was subjected to differential gene expression analyses according to BMI which was adjusted for menopausal status and tumor grade, then followed by gene set enrichment analyses. Clustering and cluster annotation were performed on the single-cell profiling data before differentially expressed genes according to BMI were identified for each of the present cell types. Results: Obesity-associated differences in the transcriptomic profile of breast tumors, which were subtle but potentially indicative of a biological relationship, were revealed by the bulk data. In both investigated subgroups, tumors from obese patients were shown to be enriched in cell cycle hallmarks. In ER-/HER2- tumors, adiposity further increased MYC signaling. We also observed different obesity-associated changes according to the ER status. Among ER+/HER2- tumors, those from obese patients were enriched in hallmarks related to inflammatory response compared to those from lean patients. In contrast, these hallmarks appeared to be enriched in the ER-/HER2- tumors from lean patients. Our investigation of the single-cell data further revealed shifts in the cell composition of tumor tissue and cell type-specific transcriptomic differences according to BMI which were more pronounced than those detected from the bulk data. ER+/HER2- tumors from obese patients have a higher frequency of immunosuppressive and pro-tumoral cell subpopulations such as dendritic cells (DC) enriched in immunoregulatory molecules (p = .03), LYVE1+ macrophages (p = .02) and myofibroblasts (p = .03) than those from lean patients. Overexpression of Cyclin D1 and CD24 was found in cancer cells in ER+/HER2- tumors from obese patients. A reduction in anti-tumor immune responses was evident with downregulation of multiple interferons in CD8+ and CD4+ T cells as well as B cells. We observed in the ER-/HER2- subgroup increased infiltration of plasmacytoid DC (p = .01), CCL2+ macrophages (p = .01) in tumors from obese versus lean patients, while fibroblasts showed an opposite tendency. Additionally, significant obesity-associated downregulation of major histocompatibility complex (MHC) molecules class I in cancer cells and MHC class II molecules in B cells could be suggestive of deficient antigen presentation and activation of cytotoxic and helper T cells. Conclusion: We highlighted the impact of obesity on the remodeling of tumor and tumor microenvironment which might generally lead to a suppression of anti-tumor immune responses, albeit potentially via diverse axes according to the ER status. Although investigation on a larger cohort is warranted, our current results suggest that obesity-associated transcriptomic changes in BC could be highly cell type-specific, hence we recommend single-cell approaches in addition to spatial multi-omics analysis to further elucidate the interplay between obesity and BC. Citation Format: Ha-Linh Nguyen, Tatjana Geukens, Marion Maetens, Karen Van Baelen, Maxim De Schepper, Coralie Poncet, Mauro Delorenzi, Marjanka K. Schmid, Emiel Rutgers, Laura Van ’t Veer, Martine Piccart, Fatima Cardoso, Giuseppe Viale, Ayse Bassez, Hanne Vos, Patrick Neven, Ines Nevelsteen, Kevin Punie, Hans Wildiers, Giuseppe Floris, Diether Lambrechts, Ann Smeets, Elia Biganzoli, François Richard, Christine Desmedt. PD4-06 Obesity-associated changes in transcriptomic profile and immune landscape of primary breast cancer revealed by bulk and single-cell gene expression data [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD4-06.

Associations of a Breast Cancer Polygenic Risk Score With Tumor Characteristics and Survival.

A polygenic risk score (PRS) consisting of 313 common genetic variants (PRS313) is associated with risk of breast cancer and contralateral breast cancer. This study aimed to evaluate the association of the PRS313 with clinicopathologic characteristics of, and survival following, breast cancer. Women with invasive breast cancer were included, 98,397 of European ancestry and 12,920 of Asian ancestry, from the Breast Cancer Association Consortium (BCAC), and 683 women from the European MINDACT trial. Associations between PRS313 and clinicopathologic characteristics, including the 70-gene signature for MINDACT, were evaluated using logistic regression analyses. Associations of PRS313 (continuous, per standard deviation) with overall survival (OS) and breast cancer-specific survival (BCSS) were evaluated with Cox regression, adjusted for clinicopathologic characteristics and treatment. The PRS313 was associated with more favorable tumor characteristics. In BCAC, increasing PRS313 was associated with lower grade, hormone receptor-positive status, and smaller tumor size. In MINDACT, PRS313 was associated with a low risk 70-gene signature. In European women from BCAC, higher PRS313 was associated with better OS and BCSS: hazard ratio (HR) 0.96 (95% CI, 0.94 to 0.97) and 0.96 (95% CI, 0.94 to 0.98), but the association disappeared after adjustment for clinicopathologic characteristics (and treatment): OS HR, 1.01 (95% CI, 0.98 to 1.05) and BCSS HR, 1.02 (95% CI, 0.98 to 1.07). The results in MINDACT and Asian women from BCAC were consistent. An increased PRS313 is associated with favorable tumor characteristics, but is not independently associated with prognosis. Thus, PRS313 has no role in the clinical management of primary breast cancer at the time of diagnosis. Nevertheless, breast cancer mortality rates will be higher for women with higher PRS313 as increasing PRS313 is associated with an increased risk of disease. This information is crucial for modeling effective stratified screening programs.

Ten-year follow-up of the observational RASTER study, prospective evaluation of the 70-gene signature in ER-positive, HER2-negative, node-negative, early breast cancer

IntroductionPrognostic gene expression signatures can be used in combination with classical clinicopathological factors to guide adjuvant chemotherapy decisions in ER-positive, HER2-negative breast cancer. However, long-term outcome data after introduction of genomic testing in the treatment decision-making process are limited. MethodsIn the prospective RASTER study, the tumours of 427 patients with cTanyN0M0 breast cancer were tested to assess the 70-gene signature (MammaPrint). The results were provided to their treating physician to be incorporated in the decision-making on adjuvant systemic therapy. Here, we report the long-term outcome of the 310 patients with ER-positive, HER2-negative tumours by clinical and genomic risk categories at a median follow-up of 10.3 years. ResultsAmong the clinically high-risk patients, 45 (49%) were classified as genomically low risk. In this subgroup, at 10 years, distant recurrence free interval (DRFI) was similar between patients treated with (95.7% [95% CI 87.7–100]) and without (95.5% [95% CI 87.1–100]) chemotherapy. Within the group of clinically low-risk patients, 56 (26%) were classified as genomically high risk. Within the clinically low-risk group, beyond 5 years, a difference emerged between the genomically high- and low-risk subgroup resulting in a 10-year DRFI of 84.3% (95% CI 74.8–95.0) and 93.4% (95% CI 89.5–97.5), respectively. Interestingly, genomic ultralow-risk patients have a 10-year DRFI of 96.7% (95% CI 90.5–100), largely (79%) without systemic therapy. ConclusionsThese data confirm that clinically high-risk, genomically low-risk tumours have an excellent outcome in the real-world setting of shared decision-making. Together with the updated results of the MINDACT trial, these data support the use of the MammaPrint, in ER-positive, HER2-negative, node-negative, clinically high-risk breast cancer patients. RegistryISRCTN71917916

Associations of a breast cancer polygenic risk score with tumor characteristics and survival.

563 Background: A polygenic risk score (PRS) consisting of 313 single nucleotide polymorphisms (PRS313) is associated with risk of breast cancer and contralateral breast cancer. One of the most promising clinical applications for the use of PRS is to provide a personalized risk assessment to individualize breast cancer screening programs. This study aimed to evaluate the association of the PRS313 with clinical-pathological characteristics and survival of breast cancer. Methods: Women of European ancestry with invasive breast cancer were included, 98,397 women from the Breast Cancer Association Consortium (BCAC) and 683 women from the MINDACT trial. Associations between PRS313 (continuous, per SD) and clinical-pathological characteristics, including the 70-gene signature for patients included in MINDACT, were evaluated with logistic regression analyses. Associations of PRS313 with overall survival (OS), breast cancer-specific survival (BCSS) and distant metastasis-free interval (DMFI) were evaluated with Cox regression analyses, adjusted for clinical-pathological characteristics and treatment. Results: The PRS313 was associated with favorable tumor characteristics. In BCAC, increasing PRS313 was mostly associated with lower grade, hormone receptor-positive tumors, and with smaller tumor size. In MINDACT, PRS313 was associated with a low risk 70-gene signature, but the association was attenuated after adjustment for clinical-pathological characteristics. In BCAC, univariable analyses showed an association of PRS313 with better survival, hazard ratio (HR) per unit SD increase of PRS313 for OS: 0.96 (95% confidence interval (CI): 0.94-0.97), for BCSS HR: 0.96 (95% CI: 0.94-0.98) and for DMFI HR: 0.98 (95% CI: 0.96-1.00). The association in the unadjusted analysis was explained by differences in clinical-pathological characteristics (and treatment) and disappeared after adjustment: OS HR: 1.01 (95% CI: 0.98-1.05), BCSS HR: 1.02 (95% CI: 0.98-1.07) and DMFI HR: 1.03 (95% CI: 0.99-1.07). Conclusions: An increased PRS313 is associated with favorable tumor characteristics but was not independently associated with prognosis. This information is crucial input for modelling effective stratified screening programs, especially in the current era of optimized (systemic) treatments. Given the significant increase in breast cancer risk associated with increasing PRS313, absolute breast cancer mortality will still be higher for women with higher PRS313.

MiRNA signatures of prognostic significance in single hormone receptor-positive breast cancer.

e12544 Background: Single hormone receptor-positive breast cancer – ER+/PgR– and ER–/PR+, is a distinct entity with vastly undiscovered biology. This study aimed at exploring miRNA profiles of primary tumors of single hormone receptor-positive phenotype and their association with overall survival (OS). Methods: The study group comprised 32 breast cancer patients, collected at 3 Polish centers, with single hormone receptor-positive phenotype, including 14 ER+/PgR– and 18 ER–/PR+ cases, thoroughly characterized for ER (clones: 1D5, EP1 and SP1) and PgR (clone: 636) expression. Expression of 798 miRNAs was profiled using nCounter Human v3 miRNA Expression Assay (NanoString) in each primary tumor sample (FFPE), data available at NCBI GEO (GSE155362). Normalized miRNAs counts were analyzed for the association with OS. Gene targets of miRNAs showing prognostic significance were identified using miRNET 2.0, while their annotation with Gene Ontology Biological Processes was determined with DAVID Bioinformatics Resources 6.8 tool. The results were validated using MINDACT trial dataset [Cardoso et al. 2016]: single hormone receptor-positive (central assessment) cases of ductal histology (including 392 ER+/PgR– and 15 ER–/PR+ cases) where analysed for the prognostic value of gene expression of the identified miRNAs targets. Results: In our cohort, 7 miRNAs showed an association with OS (log-rank test): positive for four: hsa-miR-25-3p (p=0.013), hsa-miR-150-5p (p=0.015), hsa-miR-148a-3p (p=0.038) and hsa-miR-497-5p (p=0.044); and negative for three: hsa-miR-517c-3p (p=0.017), hsa-miR-4284 (p=0.018) and hsa-miR-301a-5p (p=0.029). According to miRNET 2.0, the 4 and 3 prognostic miRNAs have 3801 and 544 gene targets, respectively. The genes targeted by positively associated miRNAs were involved in transcription regulation, vesicle-mediated transport and protein stabilization, while the targets of negatively associated miRNAs were related with mRNA polyadenylation, DNA replication and regulation of DNA-templated transcription. Next, genes targeted by most of miRNAs from either group were identified: 11 targets of positive miRNAs (CANX, CBX5, HIPK1, PDE4DIP, PPM1A, REL, SETD5, SP1, XYLT2, ZMAT3, ZNF460) and 6 targets of negative miRNAs (ARL10, DNAJC28, MTHFD1L, PRPF6, RHOF, TSPAN6). The genes were tested for the association with OS in single hormone receptor-positive subgroup of the MINDACT cohort, with the following significant findings in multivariate analysis including N stage and Ki67 status: PDE4DIP (HR=2.84, p=0.011), CBX5 (HR=2.08, p=0.026) and PRPF6 (HR=0.44, p=0.045). Conclusions: This study identifies 7 miRNAs and their gene targets with a potential prognostic significance in single hormone receptor-positive breast cancer. Thus, several miRNA-mRNA axes merit further investigation both at molecular level and in a separate patient cohort to validate their clinical utility.

Abstract DEB1-2: Con - RxPONDER: Was it all OFS?

Abstract Introduction: In Rx ponder patients with nodal involvement and a recurrence score between 0-25 were randomised to receive either chemotherapy followed by endocrine therapy or endocrine therapy alone. Patients were stratified by recurrence score (RS) 0-13 vs 14-25, menopausal status and type of axillary surgery. 50% of the patients randomised to chemotherapy received TC (4 or 6 cycles) and ovarian function suppression (OFS) was used in 16% in the ET arm and 3% in the chemotherapy plus ET arm (CET). 33% of the patients enrolled were premenopausal. The overall analysis demonstrated that patients with CET had a significantly higher iDFS at 5 years than those with ET (92.4% vs 91%); HR 0.81, p=0.026. There was a significant interaction of menopausal status and chemotherapy. 5-year iDFS was 94.2% with CET and 89% with ET (delta 5.2%); HR 0.54; p=0.0004, which was larger in the group with a RS 13-25. Because the use of OFS in the CET arm was only 3% it was hypothesised that the main effect of chemotherapy is due to ovarian function suppression. Main Part: OFS added to tamoxifen or AI is very effective in premenopausal women as shown by the SOFT and TEXT studies. The majority of women in SOFT and TEXT received chemotherapy and the effect was observed mainly in the group receiving chemotherapy (a surrogacy for high risk). Adding OFS to tamoxifen plus chemotherapy vs chemotherapy plus tamoxifen is better. The LHRH metaanalysis demonstrated that LHRH was about equally effective to chemotherapy. However, the majority of trials used 2 years LHRH, chemotherapy consisted mainly of CMF and the effect was seen in women under 40 years. The subsequent metaanalyses by the EBCTCG support chemotherapy regardless of ET and menopausal status. Anthracycline and taxane containing chemotherapy is more effective than CMF and dose-dense chemotherapy is even more effective than standard chemotherapy. Chemotherapy can induce amenorrhoea and women with chemotherapy induced amenorrhea have a better outcome than those without. Cyclosphosphamide and especially in the CMF regimen have the highest rate of amenorrhea and the main effect is seen in women between 40 and 50 years. Younger women regain menses, so the ovarian function suppression is temporarily, especially in women below 40 years. The dose of cyclophosphamide in the TC regimen, which was predominantly used in Rx-Ponder is lower than in the CMF regimen but similar to modern type chemotherapy regimen. In RX-Ponder the chemotherapy effect was seen in all premenopausal women but there was no difference of the point estimate in women between 40-50 and younger than 40 years of age. The ovarian function suppression effect is transient and women under 40 year of age tend to regain menopause and should receive an LHRH in addition. In very young women the ovarian function suppression with an LHRH analogue is about 80% leaving 20% without adequate OFS. The toxicity rate of 5 years of LHRH containing ET is high and should not be underestimated compared to 4-6 months chemotherapy. Compliance of LHRH is lower than in adjuvant chemotherapy affecting the effectiveness of adjuvant therapy. If LHRH is discontinued at 2years of LHRH the patient will receive only tamoxifen, which is too little in high risk, premenopausal women. The recurrence score mainly measures endocrine sensitivity of the tumour which does not imply chemoresistance. Nodal status remains still the most important prognostic factor and chemotherapy reduces the risk of recurrence by 30-40%.The data from Rx-Ponder are comparable to the data generated in the Mindact trial. In women younger than 50 years being at clinical high risk but with a genomic low risk tumour chemotherapy improved 8-year DDFS to 93.6% compared to 88.6% without chemotherapy (HR 0.54 95%; CI 0.30-0.98).In conclusion: Premenopausal women with node-positive HR+/HER2- breast cancer benefit from the use of chemotherapy in addition to LHRH even if the RS indicates a biological low risk. Citation Format: S Loibl. Con - RxPONDER: Was it all OFS? [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr DEB1-2.

Abstract P1-08-18: Impact of gene expression profile testing for lymph node positive (LN+) , hormone receptor positive (HR+), HER2 negative (HER2-) breast cancer (BC) patients on the use of adjuvant chemotherapy in a large community cancer center

Abstract Background: Use of gene expression profiling (GEP) is considered standard of care, in deciding use of adjuvant chemotherapy in patients with LN negative breast cancer. However, there are limited data for the use of GEP in LN+ disease. Both Mammaprint™ and Oncotype Dx 21 gene recurrence score™ (RS) have been evaluated in LN+ disease, the data are not as robust as in the LN- population. Based on data from the RXPONDER trial and the MINDACT trial, the NCCN has recently recommended the use of Oncotype Dx to help decide the utility and benefit of adjuvant chemotherapy after resection in LN- , Hormone receptor Positive (HR+), HER2 negative (HER2-) breast cancer patients. Because of the potential major impact of these data on patient management and healthcare utilization, we decided to explore the uptake and implementation of this testing at a large community cancer center in order to assess and report real world data pertaining to this novel standard of care. Methods: Database search of the Electronic Medical Records used at Ironwood Cancer Center, revealed 2455 newly diagnosed patients with early stage breast cancer during the period from 1/1/2018 till 6/1/2021. HIPAA deidentified data was extracted with inclusion criteria of newly diagnosed women with LN+ (1-3 nodes), HR+, and Her2- which yielded 403 patients. Demographics &amp; treatment data: Characteristics included menopausal status (Premenopausal 23%, Post Menopausal 77%), Surgery type (mastectomy 44%, breast conservation surgery 56%), size of primary tumor (0-1 cm 16 %, 1-2 cm 28%, 2-5 cm 43%, and &amp;gt; 5 cm 13%), LNs resected (Range 0-37, Median 4), # of LNs +(1-60%, 2-25%, 3-15%), and Tumor Grade (Grade 1-23%, 2-56%, 3-21%). GEP was performed in 62% of the patients. 49% received adjuvant chemotherapy (61% anthracycline based, 39% non anthracycline based). Of the patients tested, 41% received adjuvant chemotherapy. Adjuvant antihormonal therapy included aromatase inhibitors in 86% and Tamoxifen in 14%. 81% of the pre-menopausal patients received complete ovarian suppression. Results: Logistical Regression analysis in a non linear fashion, R2 data and Chi-square analysis was used to test the statistical significance of the observed relationship with respect to the expected relationship. The data was divided into 6 monthly intervals to allow comparison of the uptake of the test and impact on adjuvant chemotherapy decision making. There was a significant increase in GEP profile testing percentages when these intervals were compared across the years (R2 =0.69). Increase in GEP profiling was associated with lower utilization of adjuvant chemotherapy (R2= 0.84). There was a non-significant decline in the use of adjuvant chemotherapy (Chi2 NS, p value 0.22). Menopausal status, grade/size of tumor did not meet the statistical significance for the likelihood of utilization of the test. Currently multivariate analysis is being performed to examine the interplay between the numerous clinical factors on which the data was collected. This analysis will allow us to decide if we can longitudinally explore recurrence rates in each of these subsets. Conclusion: GEP has seen a significant uptake to help with adjuvant chemotherapy decision making in LN + (1-3) patients in the community cancer center setting over the last 4 years. These real world data also showed that increased testing was associated with decreased chemotherapy use which has translated to lowering health care resources and minimizing patient morbidity. Recommendations from the expert guidelines and clinical trial data have helped accelerate the use of this technology in the decision making to undergo adjuvant chemotherapy in the LN+, HR+, HER2- patients with breast cancer. Citation Format: Nisha Rao Kalmadi, Andrew Brown, Manas Sharma, Mikhail Shtivelband, Joshua Rifkind, Sujith Kalmadi, Rajesh Bagai, Emily Ho, Patricia Clark, Christopher Kellogg, Parvinderjit Khanuja. Impact of gene expression profile testing for lymph node positive (LN+) , hormone receptor positive (HR+), HER2 negative (HER2-) breast cancer (BC) patients on the use of adjuvant chemotherapy in a large community cancer center [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-08-18.

Outcome of Patients With an Ultralow-Risk 70-Gene Signature in the MINDACT Trial.

Patients with 70-gene signature ultralow-risk breast cancers have shown excellent survival in historic cohorts, including randomized trials. The ultralow-risk subgroup was characterized to help avoid overtreatment. We evaluated outcomes of ultralow-risk patients in the largest cohort to date. Of the 6,693 patients enrolled in the EORTC-10041/BIG-3-04 randomized phase III MINDACT trial, profiling revealed an ultralow-risk 70-gene signature in 1,000 patients (15%). Distant metastasis-free interval (DMFI) and breast cancer-specific survival (BCSS) were assessed in patients stratified by 70-gene signature result (high, low, and ultralow) by Kaplan-Meier analysis and hazard ratios with 95% CI from Cox regression. Median follow-up was 8.7 years. Of the ultralow-risk patients (n = 1,000), 67% were > 50 years, 81% had tumors ≤ 2 cm, 80% were lymph node-negative, 96% had grade 1 or 2 tumors, and 99% were estrogen receptor (ER)-positive. Systemic therapy was received by 84% of patients (69% endocrine therapy, 14% endocrine therapy plus chemotherapy, 1% other) and 16% received no adjuvant systemic treatment. The 8-year DMFI for ultralow-risk patients was 97.0% (95% CI, 95.8 to 98.1), which was 2.5% higher than for patients with low-risk tumors (n = 3,295, 94.5% [95% CI, 93.6 to 95.3]). The hazard ratio for DMFI was 0.65 (95% CI, 0.45 to 0.94) for ultralow versus low risk, after adjusting for clinical-pathologic and treatment characteristics. The 8-year BCSS for ultralow-risk patients was 99.6% (95% CI, 99.1 to 100). Patients with an ultralow-risk 70-gene signature have the best prognosis, distinctive from low risk, with 8-year BCSS above 99%, and very few patients developed distant metastases with an 8-year DMFI rate of 97%. These patients could be candidates for further de-escalation of treatment, to avoid overtreatment and the risk of side effects.

Outcome without any adjuvant systemic treatment in stage I ER+/HER2− breast cancer patients included in the MINDACT trial

Adjuvant systemic treatments (AST) reduce mortality, but have associated short- and long-term toxicities. Careful selection of patients likely to benefit from AST is needed. We evaluated outcome of low-risk breast cancer patients of the EORTC 10041/BIG 3-04 MINDACT trial who received no AST.Patients with estrogen receptor-positive, HER2-negative, lymph node-negative tumors ≤2 cm who received no AST were matched 1 : 1 to patients with similar tumor characteristics treated with adjuvant endocrine therapy (ET), using propensity score matching and exact matching on age, genomic risk (70-gene signature) and grade. In a post hoc analysis, distant metastasis-free interval (DMFI) and overall survival (OS) were assessed by Kaplan-Meier analysis and hazard ratios (HR) by Cox regression. Cumulative incidences of locoregional recurrence (LRR) and contralateral breast cancer (CBC) were assessed with competing risk analyses.At 8 years, DMFI rates were 94.8% [95% confidence interval (CI) 92.7% to 96.9%] in 509 patients receiving no AST, and 97.3% (95% CI 95.8% to 98.8%) in 509 matched patients who received only ET [absolute difference: 2.5%, HR 0.56 (95% CI 0.30-1.03)]. No statistically significant difference was seen in 8-year OS rates, 95.4% (95% CI 93.5% to 97.4%) in patients receiving no AST and 95.6% (95% CI 93.8% to 97.5%) in patients receiving only ET [absolute difference: 0.2%, HR 0.86 (95% CI 0.53-1.41)]. Cumulative incidence rates of LRR and CBC were 4.7% (95% CI 3.0% to 7.0%) and 4.6% (95% CI 2.9% to 6.9%) in patients receiving no AST versus 1.4% (95% CI 0.6% to 2.9%) and 1.5% (95% CI 0.6% to 3.1%) in patients receiving only ET.In patients with stage I low-risk breast cancer, the effect of ET on DMFI was limited, but overall significantly fewer breast cancer events were observed in patients who received ET, after the relatively short follow-up of 8 years. These benefits and side-effects of ET should be discussed with all patients, even those at a very low risk of distant metastasis.