Frequency of Contralateral Prophylactic Mastectomy in Breast Cancer Patients with a Negative BRCA1 and BRCA2 Rapid Genetic Test Result.

Background: There is an increasing desire for contralateral prophylactic mastectomy (CPM) among patients with unilateral breast cancer. It is unknown if risk assessment and genetic testing at the time of diagnosis will aid women in their surgical choice. We report on the uptake and predictors of CPM in women receiving a negative genetic test result for BRCA1 and BRCA2 mutations before surgery.

Methods: Women diagnosed with breast cancer between June 2013 and May 2018 were recruited from four academic health sciences centers in Toronto, Canada. Genetic counseling (risk assessment) and genetic testing was performed prior to surgery. Women were asked about their surgical preference before surgery. At 1 year post-surgery we asked what surgery was completed. This study reports on women who received a negative BRCA1/BRCA2 result.

Results: A total of 766 women with a mean age of 46 years (range 21-82) were included in the analysis. Before genetic counseling and testing, 37% of the women were undecided or leaning towards CPM; however, after receiving a negative BRCA test, 15% of the women opted for CPM. Thirty percent of women whose mother died of breast cancer elected for CPM, compared with 15% of women whose mother did not die of breast cancer (p = 0.03).

Conclusions: Women receiving a risk assessment and negative BRCA1/BRCA2 genetic test result before surgery use this information to guide their surgical decision. Uptake of CPM for women who were planning on CPM before genetic testing decreases after receiving a negative BRCA1/BRCA2 genetic test result.