A population-based analysis of germline BRCA1 and BRCA2 testing among ovarian cancer patients in an era of histotype-specific approaches to ovarian cancer prevention

Abstract

Background: Identifying female carriers of BRCA1 and BRCA2 mutations is imperative for prevention of ovarian cancer and breast cancer. There are five major histologic subtypes of ovarian cancer and high grade serous cancer (the most common) is reported in 75-100% of BRCA1 and BRCA2 mutation carriers. We examined histology-based referral to the Hereditary Cancer Program following an educational prevention campaign recommending BRCA1 and BRCA2 mutation screening for all high-grade serous cancer patients. Methods: We conducted a population-based retrospective study in the province of British Columbia, Canada that included all patients visiting the Hereditary Cancer Program for genetic counselling for BRCA1 and BRCA2 mutation between 2001 and 2014. We examined the difference in rates of BRCA1 and BRCA2 testing between serous cancer patients and endometrioid and clear cell cancer patients using a differences in differences analysis. We also calculated the mean number of family members tested for every BRCA1 and BRCA2 identified ovarian cancer patient before and after the educational campaign. Results: There were 5712 women tested for a BRCA1 and BRCA2 mutation at the HCP between 2001 and 2014, 887 of which had previously received a diagnosis of ovarian cancer. By 2013, 43% of serous cancer patients were being tested for BRCA1 and BRCA2 mutations compared with 20% of endometrioid and clear cell patients (p < 0.001). The mean number of family members tested for each BRCA1 and BRCA2 positive ovarian cancer patient increased after the educational campaign from 2.54 to 3.27 (p = 0.071), and the number of family members identified as BRCA positive also increased significantly. Conclusions: Recommendations for histology-based referral significantly increased the likelihood of serous cancer patients being tested for BRCA mutations. There was also an increase in the number of carrier tests performed for each BRCA1 and BRCA2 index ovarian cancer patient.