Breast cancer following breast reduction surgery in Sweden

Women undergoing breast reduction surgery have been reported to be at low s ubsequent risk of breast cancer, especially when the surgery is performed a fter age 40. To evaluate the ago and time-related patterns of cancer risk f ollowing surgical removal of breast tissue, we identified 31,910 women who underwent br-cast reduction surgery from 1965 to 1993 in Sweden using hospi tal discharge register data. There were 19,975 women (63 percent) under age 40 at surgery. Linkages with Swedish registries for cancer, death, and emigration were bas ed on unique national registration numbers assigned to each Swedish residen t. Cancer incidence was contrasted with that expected in the general popula tion based on age- and calendar year-specific data from the nationwide canc er registry. Overall, 161 incident breast cancers were identified during 238,765 person- years of observation (mean, 7.5 years) compared with 223.9 expected (standa rdized incidence ratio = 0.72; 95 percent confidence interval = 0.61 to 0.8 4). The reduction in risk of breast cancer was most pronounced for women wh ose operations were performed after age 50 (SIR = 0.57) and for those follo wed for more than,5 years (SIR = 0.68). Among women operated on before age 40, risk was nonsignificantly elevated within the first 5 years after surge ry (SIR = 1.47; 95 percent CI = 0.89 to 2.30) but tended to br reduced ther eafter (SIR = 0.80; 95 percent CI = 0.55 to 1.13). The magnitude of tilt: r eduction in risk thus appears directly related to age at surgery. Women followed for an average of 7.5 years after bilateral breast reduction surgery were at a statistically significant 28 percent decreased risk of b reast cancer. The current study is thus consistent with a protective effect following partial removal of breast glandular tissue.