Tubal Sterilization May Confer Some Protection Against Ovarian Cancer

As part of the Cancer and Steroid Hormone Study researchers compared data from 494 women who had ovarian epithelial cancer with data from 4238 women who had at least 1 ovary to examine the association between ovarian cancer and earlier tubal sterilization and hysterectomy. Women who experienced only a tubal sterilization had a decreased risk of ovarian cancer than never sterilized women (relative risk [RR]=0.69) but this risk was only statistically significant for women who had the sterilization 5-9 years earlier (RR=0.55). Indeed for women who underwent sterilization 15 years earlier the RR was >1. Similarly women who had only a hysterectomy had a decreased risk of ovarian cancer (RR=0.55) but this risk was only statistically significant for women who had the hysterectomy 5-9 years earlier. Specifically regardless of age at the time of hysterectomy women who underwent the hysterectomy <9 years earlier had a significantly lower risk of developing ovarian cancer than nonsterilized women (RR=0.31 for women <40 and RR=0.51 for women =or+ 40). Women who underwent the hysterectomy =or+ 10 years earlier were no less likely than nonsterilized women to develop ovarian cancer. Besides women who had a hysterectomy and 1 ovary removed were no less likely than nonsterilized women who still had both ovaries. Other analyses revealed that women sterilized at <35 years old and =or-9 years earlier were much less likely to develop ovarian cancer than nonsterilized women (RR=0.45) but the RR for women =or+ 35 years old regardless of duration was not lower than that of nonsterilized women. The researchers concluded that the 2 pelvic surgeries may have caused hormonal mechanical or circulatory changes that reduced the risk of developing ovarian cancer.