Germline ATM Testing in Hereditary Cancer Syndromes: Feedback from a Five-Year Center Cohort.

PURPOSE: Germline ATM pathogenic or likely pathogenic (P/LP) variants are increasingly recognized as clinically relevant in hereditary cancer predisposition, their integration into routine testing remains heterogeneous across countries. We describe the prevalence, tumor spectrum and relative risk associated with germline ATM P/LP variants in individuals with breast and pancreatic cancer. METHODS: We conducted a five-year retrospective (2019-2025) reanalysis of the ATM gene in 1,707 probands tested with hereditary breast and ovarian cancer (HBOC) or pancreatic cancer panels in our center. For all probands that underwent targeted ATM reanalysis, relative risks (RR) and odds ratios (OR) were calculated. Family-based segregation was performed when possible. RESULTS: Targeted ATM re-analysis identified 33 additional probands with P/LP variants, increasing diagnostic yield from 7.3% to 9.1% in HBOC and from 4.3% to 9.7% in pancreatic cancer. Among 22 breast-cancer probands, mean age at diagnosis was 47 years. Case-control comparison yielded OR 3.85 (95% CI 2.43-6.08; P=8.5×10-9) for breast cancer and OR 15.81 (95% CI 6.31-39.66; P=4.0×10-9) for pancreatic cancer. CONCLUSION: This work strengthens the role of ATM in cancer predisposition panels and supports its inclusion in French national hereditary cancer panel recommendations, together with implementation of appropriate surveillance and counseling for individuals harboring ATM P/LP variants.