Rapid Genetic Testing for BRCA1 and BRCA2 Mutations at the Time of Breast Cancer Diagnosis: An Observational Study.

Background: This study aimed to evaluate the impact of rapid genetic testing (RGT) for BRCA1 and BRCA2 at the time of breast cancer diagnosis on treatment choices. Bilateral mastectomy for the treatment of breast cancer in women with a BRCA1 or BRCA2 mutation offers a reduction in the risk of contralateral breast cancer. It is unclear whether offering RGT at the time of breast cancer diagnosis has an impact on women's surgical decision-making.

Methods: Women with breast cancer diagnosed between June 2013 and May 2018 were recruited from four academic health sciences centers in Toronto, Canada. The participants completed a questionnaire before genetic testing, then one week and one year after disclosure of the genetic test result. Before surgery, RGT was performed. Diagnostic, pathologic, and treatment data were compared between those with and those without a BRCA mutation.

Results: The study enrolled 1007 women who consented to RGT. The mean age of the participants was 46.3 years, and the median time to result disclosure was 10 days. A BRCA mutation was found in 6% of the women. The women with a BRCA mutation were significantly more likely to elect for bilateral mastectomy than the women without a BRCA mutation (p < 0.0001). Of the BRCA-positive patients, 95.7% reported that they used their genetic test result to make a surgical decision.

Conclusions: The women provided with RGT at the time of breast cancer diagnosis use the genetic information to make treatment decisions, and the majority of those identified with a BRCA mutation elect for a bilateral mastectomy.