Routine germline BRCA1 and BRCA2 testing in patients with ovarian carcinoma: analysis of the Scottish real-life experience

Abstract

Objective: To determine the rates of germline BRCA1 and BRCA2 mutations in Scottish patients with ovarian cancer, before and after a change in testing policy. Design: Retrospective cohort study. Setting: Four cancer/genetics centres in Scotland. Population: Patients with ovarian cancer undergoing germline BRCA1 and BRCA2 (gBRCA1/2) sequencing before 2013 (under the ‘old criteria’, with selection based solely on family history), after 2013 (under the ‘new criteria’, with sequencing offered to newly presenting patients with non-mucinous ovarian cancer), and in the ‘prevalent population’ (who presented before 2013, but were not eligible for sequencing under the old criteria but were sequenced under the new criteria). Methods: Clinicopathological and sequence data were collected before and for 18 months after this change in selection criteria. Main outcome measures: Frequency of germline BRCA1, BRCA2, RAD51C, and RAD51D mutations. Results: Of 599 patients sequenced, 205, 236, and 158 were in the ‘old criteria’, ‘new criteria’, and ‘prevalent’ populations, respectively. The frequency of gBRCA1/2 mutations was 30.7, 13.1, and 12.7%, respectively. The annual rate of gBRCA1/2 mutation detection was 4.2 before and 20.7 after the policy change. A total of 48% (15/31) ‘new criteria’ patients with gBRCA1/2 mutations had a Manchester score of <15 and would not have been offered sequencing based on family history criteria. In addition, 20 patients with gBRCA1/2 were identified in the prevalent population. The prevalence of gBRCA1/2 mutations in patients aged >70 years was 8.2%. Conclusions: Sequencing all patients with non-mucinous ovarian cancer gives a much higher annual gBRCA1/2 mutation detection rate, with the frequency of positive tests still exceeding the 10% threshold upon which many family history-based models operate. Tweetable abstract: BRCA sequencing all non-mucinous cancer patients increases mutation detection five fold.