Hysterectomy, tubal sterilization, and the risk of breast cancer.

Studies suggest that hysterectomy and tubal sterilization may alter the function of the remaining ovaries. Conceivably, this effect could alter breast cancer risk. To investigate whether these surgeries affect breast cancer risk, the authors analyzed data collected between December 1, 1980, and April 30, 1983, in a population-based, case-control study of women aged 20-54 years, the Cancer and Steroid Hormone Study. Compared with never-sterilized women, women with hysterectomy and no remaining ovaries had a decreased risk of breast cancer (relative risk (RR) = 0.7, 95% confidence interval (CI) = 0.6-0.8). Risk was lowest in women who had their surgery before age 40 years or 15 or more years in the past; surgery at an early age provided greater protection than surgery in the distant past. Hysterectomy with one or two remaining ovaries was also inversely associated with breast cancer risk (RR = 0.8, 95% CI = 0.7-0.9), but no relation was found with age at surgery or time since surgery. Women with tubal sterilization had a slightly increased risk of breast cancer, which was of borderline statistical significance (RR = 1.2, 95% CI = 1.0-1.3). However, no relation was found with age at surgery or time since surgery. The data suggest that hysterectomy with bilateral oophorectomy decreases the breast cancer risk in women aged less than 55 years, possibly by curtailing ovarian function at a critical period. However, neither hysterectomy without bilateral oophorectomy nor tubal sterilization appears to substantially alter breast cancer risk in women of this age.