Tubal sterilization and breast cancer incidence: results from the cancer prevention study II nutrition cohort and meta-analysis.

Tubal sterilization is a common form of contraception in the United States and is hypothesized to be associated with a lower risk of breast cancer. However, prior observational studies have reported inconsistent results. We investigated the association between tubal sterilization and breast cancer risk among 77,249 postmenopausal, cancer-free women in the Cancer Prevention Study II (CPS-II) Nutrition Cohort, enrolled in 21 states in the United States during 1992-1993. During 15 years of follow-up through June 30, 2007, 4,084 invasive breast cancer cases were diagnosed. Multivariable Cox proportional hazard regression was used to estimate hazard ratios and 95% confidence intervals. A meta-analysis including the CPS-II Nutrition Cohort results with other published results from 4 case-control studies and 3 prospective studies was conducted to provide a summary estimate for the association between tubal sterilization and breast cancer risk. In the CPS-II Nutrition Cohort, tubal sterilization was not associated with breast cancer incidence (multivariable-adjusted hazard ratio = 1.08, 95% confidence interval: 0.97, 1.20). Associations stratified by year of tubal sterilization, age, and time since surgery were also null. The meta-analysis also found no association between tubal sterilization and breast cancer risk (odds ratio = 0.97, 95% confidence interval: 0.84, 1.09). Tubal sterilization does not appear to be associated with breast cancer risk.