Prophylactic mastectomy cuts breast cancer riskBMJ 1999; 318 doi: https://doi.org/10.1136/bmj.318.7178.216a (Published 23 January 1999) Cite this as: BMJ 1999;318:216
Prophylactic bilateral mastectomy dramatically reduces the likelihood of developing breast cancer in women with a strong family history of the disease, according to the first study to clarify the value of this previously controversial approach (New England Journal of Medicine 1999;340:77-84).
The findings, from a retrospective study of 639women who had their breasts removed between 1960and 1993,are being regarded as the most reliable information available on the long term effectiveness of the procedure. A total of 214women assessed as being at high risk of developing breast cancer because of their positive family histories, and 425assessed as being at moderate risk, were included in the study. A control group including sisters of high risk women was used to predict the number of breast cancers expected in the absence of bi-lateral mastectomy.
Breast cancer was eventually diagnosed in only 1.4% (3of 214) of women who underwent prophylactic bilateral mastectomy, compared with 38.7% (156of 403) of the control group. Among the 425women with a moderate risk of breast cancer who underwent surgery, a statistical model predicted that breast cancers would be expected to occur in 37.4% during follow up, but the actual finding was less than 1%.
Women in the study were aged 18to 79when they had surgery, with a median age of 42.Half of the women had had surgery 14or more years before the study, and all had had it at least five years earlier.
The study, from the Mayo Clinic in Rochester, Minnesota, is “the first credible calculation” of the benefits of prophylactic mastectomy, according to Dr Patrick Borgen, chief of breast surgery at the Memorial Sloan Kettering Cancer Center in New York, who was not involved in the study. But he cautioned that the results should not be used to pressure women into having prophylactic mastectomies.