The Incidence Of Breast Cancer In Ovarian Cancer Patients With BRCA Mutations: A Multicentre Retrospective Cohort Study

Abstract

Introduction/Background Germline BRCA mutations (gBRCA) are the most common hereditary cause for women's cancers, accounting for 8-14% of ovarian and 2-3% of breast cases. Risk reducing bilateral mastectomy (RRBM) reduces the incidence of breast cancer in gBRCA carriers by 90-95%. However, the effectiveness of this surgery needs to be considered against surgical morbidity, patient acceptance, improvements in cancer surveillance, incidence of breast cancer after ovarian cancer in gBRCA carriers and impact of maintenance polymerase inhibitors (PARPi). Methodology We performed a retrospective review of 527 consecutive patients with gBRCA1/2 associated ovarian cancer, 2006-2023, from 5 oncology centres (4xUK, 1xIsrael). Data collected included demographics, gBRCA1/2 status, oncological treatment, breast cancer diagnosis, RRBM and overall survival. Results Median age at ovarian cancer diagnosis was 55 (range:28-88) years; 331 (62.8%) had gBRCA1, 183 (34.7%) gBRCA2 and 13 (2.5%) gBRCA1/2 of unknown significance. Breast cancer diagnosis preceded ovarian cancer in 104 (19.7%) and there were also 8 (1.5%) synchronous cases. Breast cancer was diagnosed after ovarian cancer in 18 patients, median time between diagnoses was 2 years, 3 patients received first-line PARPi maintenance and 6 at disease recurrence. The 1-, 3- and 5-year breast cancer rates were 1.4%, 2.5% and 2.9%, respectively, with 84.5 months median follow-up. There was no evidence of worse overall survival in those with subsequent breast cancer (n=18) compared to controls with no breast cancer diagnosis (n=36), matched 1:2 by ovarian cancer stage (I&II/III&IV) and time period (within 2 years): medians 116.9 (95%CI:78.2-155.6) and 102.4 (95%CI:71.8-133.0) months respectively. Conclusion There is low incidence of breast cancer diagnosis in women who have previously undergone treatment for gBRCA mutated ovarian cancer. Our results are similar to literature from the United States and Israel. These data will help to counsel patients regarding breast cancer surveillance as an alternative to RRBM in ovarian cancer survivors.