Efficacy of contralateral prophylactic mastectomy in women with a personaland family history of breast cancer

Purpose : To estimate the efficacy of contralateral prophylactic mastectomy in women with a personal and family history of breast cancer. Patients and Methods: We followed the course of 745 women with a first brea st cancer and a family history of breast and/or ovarian cancer who underwen t contralateral prophylactic mastectomy at the Mayo Clinic between 1960 and 1993. Family history information and cancer follow-up information were obt ained from the medical record, a study-specific questionnaire, and telephon e follow-up. Life-tables for contralateral breast cancers, which consider a ge at first breast cancer, current age, and type of family history, were us ed to calculate the number of breast cancers expected in our cohort had the y not had a prophylactic mastectomy. Results: Of the 745 women in our cohort, 388 were premenopausal (age < 50 y ears) and 357 were post-menopausal. Eight women developed a contralateral b reast cancer. Six events were observed among the premenopausal women, compa red with 106.2 predicted, resulting in a risk reduction of 94.4% (95% confi dence interval [CI], 87.7% to 97.9%). For the 357 postmenopausal women, 50. 3 contralateral breast cancers were predicted, whereas only two were observ ed, representing a 96.0% risk reduction (95% Cl, 85.6% to 99.5%). Conclusion: The incidence of contralateral breast cancer seems to be reduce d significantly after contralateral prophylactic mastectomy in women with a personal and family history of breast cancer. (C) 2001 by American Society of Clinical Oncology.