BACKGROUND: Risk-reducing mastectomy is one option for women with hereditary breast and ovarian cancer to reduce the risk of breast cancer. PATIENTS AND METHODS: We analyzed data of the Japanese Organization of Hereditary Breast and Ovarian Cancer on women who were diagnosed as hereditary breast and ovarian cancer by BRCA germline genetic testing between 2010 and 2019 to reveal the rate and likelihood of risk-reducing mastectomy. RESULTS: There were 412 women with BRCA1, 271 with BRCA2 and 4 with both female pathogenic variants. Ninety (13.1%) received risk-reducing mastectomy. The rates of risk-reducing mastectomy were statistically significantly higher in women with BRCA1 pathogenic variants than BRCA2, in women who had breast cancer than those who did not, in women with a breast cancer family history than in those without, in mothers than in those without children, in women who were receiving surveillance with MRI than those who were not and in women who received risk-reducing salpingo-oophorectomy than in those who did not on univariate analyses. The ages when they received the genetic testing were statistically significantly younger in the women receiving risk-reducing mastectomy than those who did not receive it. The women with BRCA1 pathogenic variants, personal history of breast cancer, mothers, those receiving MRI surveillance and younger women were independently significantly more likely to receive risk-reducing mastectomy based on multivariate analysis. CONCLUSIONS: The rate of risk-reducing mastectomy was not high in Japan; however, risk-reducing surgery was approved by the Japanese National Medical Insurance for hereditary breast and ovarian cancer patients with breast and/or ovarian cancer in 2020, so this rate will increase.
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