Genital powder use and risk of uterine cancer: A pooled analysis of prospective studies.

When powder is applied to the genital area, it has the potential to reach internal reproductive organs and promote carcinogenesis by irritating and inflaming exposed tissues. Although many studies have considered the association between genital powder use and ovarian cancer risk, the relationship between genital powder use and uterine cancer is less well-studied. We pooled data from four large, prospective cohorts (the Nurses' Health Study, the Nurses' Health Study II, the Sister Study and the Women's Health Initiative - Observational Study). We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for prespecified confounders. In total, 209 185 women were included, with 37% reporting ever genital powder use. Over a mean 14.5 years of follow-up, 3272 invasive uterine cancers were diagnosed. There was no overall association between ever genital powder use and uterine cancer (HR = 1.01, 95% CI: 0.94-1.09), with little difference observed for frequent (≥1 times/week) vs never use (HR = 1.05, 95% CI: 0.95-1.16; P-for-trend = .46). Long-term use (>20 years; HR = 1.12, 95% CI: 0.96-1.31; P-for-trend = 0.14) was associated with a small, but not statistically significant, increase in risk, compared to never use. There were not clear differences by uterine cancer histologic subtypes or across strata of relevant covariates, including race/ethnicity, follow-up time, menopausal status and body mass index. The results of this large, pooled analysis do not support a relationship between the use of genital powder and uterine cancer, although the positive associations observed for long-term use may merit further consideration.