Abstract PO4-09-01: Survival of patients harboring a germline ATM pathogenic/likely pathogenic variant and diagnosed with breast cancer: A case-control study

Abstract Introduction: Patients harboring a pathogenic/likely pathogenic variant (PV/LPV) in ATM present an increased lifetime risk of developing breast cancer (BC). The survival outcomes of these patients are not well-known. Methods: Retrospective, multicentric case-control study. Case group included patients with stage I-III breast cancer harboring a PV/LPV in ATM. Control group included patients with stage I-III breast cancer with a negative germline BC multigene panel testing including ATM gene analysis. Clinical outcomes defined as locoregional relapse-free survival (RFS), distant RFS and breast cancer specific survival were compared between cases and controls. Case group was obtained from five hereditary cancer units and control group was obtained from a sporadic clinic-based cohort. Cases and controls were matched 1:2 by stage, molecular subtype by immunohistochemistry, age at BC diagnosis and year of BC diagnosis. Baseline continuous variables were presented as mean and standard deviation and comparison was performed with Student´s t-test. Baseline categorical variables were presented with number and percentage and comparison were performed using chi-square test. Survival analyses were estimated by Kaplan-Meier curves, the comparison of survival was tested by stratified log-rank testing. Cox proportional hazards model was used to estimate the hazard ratio and confidence intervals. Results: We identified 64 patients (p) with an ATM PV/LPV and 120 controls. Median age at diagnosis was 47 years (28-84) and 46 years (25-88), respectively. The main tumoral characteristics in both groups were ductal (87.5% and 83.5%), luminal B-HER2 negative (37.5% and 45.8%) with histological grade II (54.7% and 58.5%) tumors. Majority of tumors in both groups were diagnosed at stage II (53.1% and 54.2%). Differences between groups were observed in first-degree BC family history (39p (61.9%) vs 51p (43.6%); p=0.02); frequency of multicentric/multifocal tumors (15p (25%) vs 13p (11.1%); p=0.018); contralateral breast cancer (16p (25%) vs 8p (6.7%); p=0.0004) and type of surgery (46.8% conservative surgery in cases and 69.2% in controls; p< 0.001). The result of the germline genetic study was not available for all patients before surgery. Baseline characteristics are summarized in Table 1. With a median follow-up of 6.7 years, we observed more locoregional recurrence and distant recurrence in the control group (ipsilateral local or lymphatic recurrence: 0p (0%) vs 15p (12.5%); p=0.078; metachronic contralateral breast cancer: 7p (12.7%) vs 3p (2.6%); p=0.02; distance recurrence 5p (7.8%) vs 24p (20%); p=0.03. No differences between groups were observed in BC-specific survival analysis, with a median BC-specific survival of 6.24y (4.67-12.1) in patients with ATM and 6.68y (6.12-7.94) in the control group (HR: 1.21 (0.88-1.65); p=0.24). Conclusions: Patients with BC harboring a germline ATM PV/LPV had more multifocal and multicentric disease at diagnosis; and more synchronous and metachronous contralateral BC compared to controls, with no differences in BC-specific survival. Further studies in a larger cohort are warranted to analyze sensitivity to systemic therapies. Table 1. Baseline characteristics of cases and control groups. ER (Estrogen Receptor) positive if > or equal to 1%; PR (Progesterone Receptor) positive if > or equal to 1%; HER2 (Human epidermal growth factor receptor-2); ChTh: Chemotherapy; SLNB: Sentinel Lymph Node Biopsy; AL: Axillar lymphadenectomy Citation Format: Mara Cruellas, Ariadna Roqué, Nuria Dueñas, Iris Teruel, Noemí Tuset Der-Abrain, Alejandra Rezqallah, Víctor Navarro, Laia Joval-Ramentol, Maite Torres, Cristina Saura, Joan Brunet, Judith Balmaña. Survival of patients harboring a germline ATM pathogenic/likely pathogenic variant and diagnosed with breast cancer: A case-control study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-09-01.