Current Status and Challenges of BRCA1 and BRCA2 Genetic Testing for Hereditary Breast and Ovarian Cancer in Japan.

Background/Aim: testing and the prevalence of pathogenic variants at our institution. Patients and Methods: genetic testing between July 2018 and September 2024. Patients were classified into three groups: a newly diagnosed group (diagnosed after the introduction of insurance coverage for HBOC testing in April 2020), a postoperative follow-up group (diagnosed before April 2020 and tested during follow-up), and a companion diagnostic group for metastatic breast cancer. Clinicopathological characteristics, fulfilled eligibility criteria, and positivity rates were compared. Results: , n=22). Variant positivity rates were 10.1% in the newly diagnosed group, 20.0% in the postoperative follow-up group, and 12.5% in the companion diagnostic group. Conclusion: variants in the postoperative follow-up group suggests that genetic testing for hereditary breast and ovarian cancer (HBOC) may be underutilized among eligible breast cancer patients during follow-up. Proactive testing recommendations by healthcare providers and improved patient understanding are essential.