Breast Cancer Prevention (PDQ®): Prevention - Health Professional Information [NCI] - Description of Evidence
Incidence of Outcomes Per 1,000 Women continued...
A retrospective cohort study was conducted to evaluate the impact of bilateral prophylactic mastectomy on the subsequent occurrence of breast cancer among women at high and moderate risk of breast cancer on the basis of family history. Most women in this retrospective series (90%) had undergone subcutaneous rather than total mastectomy, which is the procedure of choice for maximum breast tissue removal. Median follow-up after surgery was 14 years. All women included in the report had some family history of cancer and were classified as high risk or moderate risk for breast cancer based on the pattern of breast cancer in the family. Expected cases of breast cancer were estimated for moderate- and high-risk women using the Gail model and the observed rates of breast cancer among sisters of the probands. The reduction in risk for moderate-risk women was 89%; for high-risk women, the reduction ranged from 90% to 94% depending on the method used to calculate expected rates of breast cancer. The reduction in risk of death from breast cancer ranged from 100% among moderate-risk women to 81% among high-risk women. Information on BRCA1 or BRCA2 mutation status was not known. Although this study provides the best evidence available to date that prophylactic surgery offers benefits despite the fact that some breast tissue remains postsurgery, some factors may bias the estimate of benefit. Criteria used to classify women at high risk would include women from families misclassified as having an autosomal-dominant inherited pattern and women from inherited-syndrome families who are not at high risk because they did not inherit the susceptibility genotype. These factors may tend to overestimate the benefits of prophylactic surgery. Most of the women, however, who underwent prophylactic surgery would never have gone on to develop breast cancer. Thus, many were treated for the few who truly benefited by having their breast cancer prevented. Among the 425 moderate-risk women who had prophylactic mastectomy, the estimated number of breast cancer cases expected to occur was 37.4; among the 214 high-risk women, the estimates ranged from 30.0 to 52.9, depending on the model used to estimate breast cancer occurrence. Thus, bilateral prophylactic mastectomy as an option for women should be considered in association with cancer risk assessment and counseling regarding all the available preventive options, which now include tamoxifen as a preventive agent.
Studies of the harms of prophylactic mastectomy have been retrospective. Most women reported relief of anxiety about breast cancer, and few were dissatisfied with their choice to undergo the procedure. A higher dissatisfaction rate occurred among women who chose reconstruction over those who did not.
Women at high risk due to BRCA1 or BRCA2 gene mutations who had prophylactic oophorectomies to prevent ovarian cancer were found to have a lower incidence of breast cancer than age-matched mutation carriers who did not undergo prophylactic oophorectomy.[110,111,112] The reported reductions in RR were approximately 50%. These observational studies, however, are confounded by selection bias, family relationships between patients and controls, indications for oophorectomy, and inadequate information about hormone use. A prospective cohort study has confirmed a reduction in breast cancer risk by about 50% with prophylactic oophorectomy, and a greater reduction in BRCA2 mutation carriers than in BRCA1 carriers.