Women with BRCA variants have a high lifetime risk of developing breast and ovarian cancer. The aim of this study was to investigate the standard incidence ratios (SIR) for breast and ovarian cancer and standard mortality ratios (SMR) in a population-based cohort of women in Western Sweden, under surveillance and after risk reducing surgery. Women who tested positive for a BRCA variant between 1995-2016 (n = 489) were prospectively registered and followed up for cancer incidence, risk reducing surgery and mortality. The Swedish Cancer Register was used to compare breast and ovarian cancer incidence and mortality with and without risk reducing surgery for women with BRCA variants in comparison to women in the general population. SIR for breast cancer under surveillance until risk-reducing mastectomy (RRM) was 14.0 (95% CI 9.42-20.7) and decreased to 1.93 (95% CI 0.48-7.7) after RRM. The SIR for ovarian cancer was 124.6 (95% CI 59.4-261.3) under surveillance until risk reducing salpingo-oophorectomy (RRSO) and decreased to 13.5 (95% CI 4.34-41.8) after RRSO. The SMR under surveillance before any risk reducing surgery was 5.56 (95% 2.09-14.8) and after both RRM and RRSO 4.32 (95% CI 1.62-11.5). Women with cancer diagnoses from the pathology report after risk reducing surgery were excluded from the analyses. Risk reducing surgery reduced the incidence of breast and ovarian cancer in women with BRCA variants. However, overall mortality was significantly increased in comparison to the women in the general population and remained elevated even after risk reducing surgery. These findings warrant further research regarding additional measures for these women.
Keywords: BRCA1; BRCA2; hereditary breast cancer; hereditary ovarian cancer; risk reducing mastectomy; risk reducing salpingo-oophorectomy; survival.