Breast cancer risk in relation to amount of tissue removed during breast reduction operations in Sweden.

[BACKGROUND] Women who undergo breast reduction operations have substantially lowered risks of breast cancer, and the reasons remain unclear. The current investigation attempted to assess whether the reduction in breast cancer risk was related directly to the amount of breast tissue removed.

[METHODS] Medical record retrieval was attempted for 161 breast cancer patients in a Swedish cohort of 31,910 women who had had breast reduction surgery and for 483 women who had not developed breast cancer. Information on amount of breast tissue removed was abstracted along with other factors that influence breast cancer risk. Odds ratios of developing breast cancer were calculated based on amount of breast tissue removed.

[RESULTS] The amount of tissue removed was a significant predictor of risk, as subjects in the highest quartile of tissue removal had a significantly lower risk than those in the lowest quartile. Considering the total amount of tissue removed (both breasts), subjects with > or = 1600 versus < 800 grams removed had an odds ratio (OR) of 0.24 [95% confidence interval (CI) 0.1-0.5]. This relation persisted after adjustment for other breast cancer risk factors and was apparent within every subgroup examined.

[CONCLUSIONS] The finding that breast cancer risk was reduced in proportion to the amount of tissue removed should be reassuring to women who are considering breast reduction procedures and to women who are electing to have bilateral total prophylactic mastectomies because of a strong genetic predisposition.