Breast cancer after ovarian cancer in BRCA1 and BRCA2 pathogenic variant heterozygotes: lower rates for 5-years post chemotherapy

Background
The identification of germline BRCA1/BRCA2 pathogenic variants (PV) infer high remaining lifetime breast/ovarian cancer risks, but there is paucity of studies assessing breast cancer risk after ovarian cancer diagnosis.

Methods
We reviewed the history of breast cancer in 895 PV heterozygotes (BRCA1=541). Cumulative annual breast cancer incidence was assessed at 2,5,10 and >10 years following ovarian cancer diagnosis date.

Results
Breast cancer annual rates were evaluated in 701 assessable women with no breast cancer at ovarian diagnosis (BRCA1=425). Incidence was lower at 2years (1.18%) and 2-5years (1.13%), but rose thereafter for BRCA1 with incidence post 10years in excess of 4% annually. Breast cancer pathology in BRCA1 PV heterozygotes showed less high-grade triple negative breast cancer and more lower grade hormone-receptor positive cancer than women with no prior ovarian cancer. In the prospective cohort from ovarian cancer diagnosis <4% of all deaths were caused by breast cancer, although 50% of deaths in women with breast cancer post-ovarian cancer diagnosis were due to breast cancer.

Conclusion
Women can be reassured that incidence of breast cancer post-ovarian diagnosis is relatively low. It appears likely that this effect is due to platinum-based chemotherapy. Nonetheless women need to be aware that incidence increases thereafter, especially after 10 years.