Risk of de novo cancer after premenopausal bilateral oophorectomy.

Background Hysterectomy is one of the most frequent gynecologic surgeries in the United States. Women undergoing hysterectomy commonly are offered bilateral oophorectomy for ovarian and breast cancer prevention. Although bilateral oophorectomy may dramatically reduce the risk of gynecologic cancers, some studies suggested that bilateral oophorectomy may be associated with an increased risk of other types of cancer, such as lung cancer and colorectal cancer. However, the results are conflicted. Objective To study the association between bilateral oophorectomy and the risk of subsequent cancer of any type. Study design This population-based cohort study included all premenopausal women who underwent bilateral oophorectomy for a nonmalignant indication before the age of 50 years between January 1, 1988 and December 31, 2007 in Olmsted County, Minnesota, and a random sample of age-matched (±1 year) referent women who did not undergo bilateral oophorectomy. Women with cancer before oophorectomy (or index date) or within 6 months after the index date were excluded. Time-to-event analyses were performed to assess the risk of de novo cancer. Cancer diagnosis and type were confirmed using medical record review. Results Over a median follow-up of 18 years, the risk of any cancer did not significantly differ between 1562 women who underwent bilateral oophorectomy before natural menopause and 1610 referent women (adjusted hazard ratio (HR), 0.82, 95% CI, 0.66-1.03). However, women who underwent bilateral oophorectomy had a decreased risk of gynecologic cancers (HR, 0.15; 95% CI, 0.06-0.34) but not of non-gynecologic cancers (HR, 0.99; 95% CI, 0.78-1.26). In particular, the risk of breast cancer, gastrointestinal cancer, and lung cancer did not differ between these two cohorts. Use of estrogen therapy through the age of 50 years in women who underwent bilateral oophorectomy did not modify the results. Conclusions Women who underwent bilateral oophorectomy before menopause have a reduced risk of gynecologic cancer but not of other types of cancer including breast cancer. Women at average risk of ovarian cancer should not consider bilateral oophorectomy for the prevention of breast cancer or other non-gynecologic cancers.