Powder analysis.

Top Line: It’s hypothesized that talcum powder-induced inflammation and/or chemical exposure in the reproductive tract leads to malignancy.

The Study: This huge study pools prospectively collected data from over 250,000 women in 4 large cohort studies: the Nurses’ Health Study, the Nurses’ Health Study II, the Sisters Study, and the Women’s Health Initiative Observational Study. While not a question that would have come to our minds, all happened to ask women about the frequency of use of powder on their genitals. Because women were questioned long before a potential association was posited, recall bias isn't as big an issue as in recent case-control studies. Over a third of women used genital powder, with 22% using it frequently (i.e., at least once per week) and 10% using it long-term. Overall, there was no association with either the frequency or duration of powder use and the cumulative risk of ovarian cancer by age 70 (HR 1.08, 95% CI 0.99-1.17). However, among the pertinent subset of women with an intact reproductive tract, the HR was 1.13 (95% CI 1.01-1.26) and an even higher at 1.19 (95% CI 1.03-1.37) if they used powder frequently. To complicate matters, the difference between hazard ratios for women with patent and non-patent reproductive tracts was not significant. This led the authors to conclude that there was no statistical—and certainly no significant—association between powder use and cancer.  But also recognize that even their 250K+ participant cohort was underpowdered to detect any potential extremely small increase in risk, which may still be relevant when a third of the female population is using the product. It is further pointed out that the effect size in the patent reproductive tract cohort is so small that it “should not be selectively highlighted by the statistically unsophisticated reader as evidence of a relationship.” Missouri, those are fightin’ words.

TBL: In this huge cohort study, the use of talcum powder on the perineum was not clearly associated with an increased risk of ovarian cancer. | O’Brien, JAMA 2020