Perineal powder use and risk of endometrial cancer in postmenopausal women

Most known endometrial cancer risk factors involve genetics or exposure to unopposed estrogens; less is known about risk due to environmental exposures. While several studies have found an increased risk of ovarian cancer associated with perineal powder use, only two studies have addressed perineal powder use and endometrial cancer risk. We used Cox proportional hazards regression to examine the association between perineal powder use and endometrial cancer risk using the Women's Health Initiative Observational Study Research Materials obtained from the National Heart, Lung, and Blood Institute Biological Specimen and Data Repository Coordinating Center. Of the 48,526 women in our primary analysis, 25,181 (52 %) reported ever use of perineal powder. During 364,134 person-years of follow-up, 447 participants were diagnosed with endometrial cancer. Ever use of perineal powder was not associated with increased risk of endometrial cancer (multivariable-adjusted hazard ratio, 1.06; 95 % confidence interval, 0.87-1.28). External use of powder on the genitals and/or on sanitary napkins was also not significantly associated with risk of endometrial cancer. However, use of powder on a diaphragm for twenty or more years was associated with a threefold increase in risk of endometrial cancer compared to women who never used perineal powder (multivariable-adjusted hazard ratio, 3.06; 95 % CI, 2.00-4.70). Any duration of external use of perineal powder was not associated with increased risk of endometrial cancer; however, long-term use of powder on a diaphragm may increase the risk of endometrial cancer.