Hysterectomy, oophorectomy, and subsequent ovarian cancer risk.

OBJECTIVE: To analyze the relation between hysterectomy with or without oophorectomy and the risk of subsequent ovarian cancer. METHODS: We have conducted a case-control study since 1983 in a network of general and university hospitals in the greater Milan area. The cases were 953 women aged less than 75 years with histologically confirmed epithelial ovarian cancer. Women younger than 75 years residing in the same geographic area and admitted for acute conditions to the same network of hospitals where the cases had been identified were eligible as controls. Potential controls were excluded if they had been admitted for gynecologic, hormonal, or neoplastic diseases or had previously undergone bilateral oophorectomy. A total of 2758 controls were interviewed. RESULTS: Fifty-two cases (5.5%) and 215 controls (7.8%) reported a history of hysterectomy, including eight cases and 38 controls who also reported unilateral oophorectomy. In comparison with women with intact uterus and ovaries, the age-adjusted relative risk (RR) was 0.7 in both women who reported hysterectomy alone (95% confidence interval [CI] 0.5-0.9) and in those reporting hysterectomy plus unilateral oophorectomy, though the latter finding was not statistically significant (95% CI 0.3-1.4). The risk of ovarian cancer was inversely related with time from hysterectomy. Compared with women reporting no pelvic surgery, the RR was 0.9 (95% CI 0.4-1.7), 0.7 (0.3-1.6), 0.7 (0.3-1.4), and 0.5 (0.3-0.8), respectively, in women reporting hysterectomy within 4 years or less and 5-9, 10-14, and 15 years or more before interview. CONCLUSION: Hysterectomy approximately halves the risk of ovarian cancer, possibly because of altered ovarian blood flow or the opportunity that hysterectomy provides for examining the ovaries.