Objective Universal genetic testing has become increasingly important in the management of women with epithelial tubo-ovarian and peritoneal carcinoma. Worldwide, the reported rates of deleterious BRCA mutation rate vary between 12–15%. We wanted to evaluate the mutation rate in our population considering its specific genetic background (French Canadian ascent).
Method Mainstreaming genetic testing was implemented in our service in Mai 2017 and offered to all patients with epithelial tubo-ovarian or peritoneal carcinomas, except mucinous and borderline tumors. The data was prospectively collected in a database and retrospectively analyzed.
Results A total of 214 patients were tested in our center, 169 (79%) were high grade serous carcinomas (HGSC). Overall, 137 patients had no mutation (64%). Deleterious BRCA 1/2 mutations were observed in 10 patients (4,7%), 4 BRCA1 and 6 BRCA2, nearly all were in HGSC (9). Other non BRCA-mutations (ATM, RAD51C, RAD51D, BRIP1, CDH1, MRE11, MSH6, MUTYH, PALB2 and PMS2) were observed in an additional 18 patients (8,4%): 16 HGSC, 1 endometrioid and 1 carcinosarcoma. VUS were seen in 57 patients (26,7%) of which 4 were BRCA1/2 VUS. No deleterious mutations were identified in clear cell carcinomas and seen in only one low grade serous carcinoma.
Conclusion In our specific French Canadian population, the deleterious germline BRCA mutation rate was surprisingly low (4,7%), less than half the rate reported in the literature. Based on Health Canada’s current approval, only a small proportion of our patients could access PARPi therapy. Hopefully canadian indications for PARPi will soon include non-BRCA and somatic mutations.
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