The question of whether the use of talc powder around the genital area causes ovarian cancer has long frustrated researchers. At the heart of the debate is the question of how to study the issue: Do you ask women who have the disease to recall their past grooming routines, or do you mine massive databases that documented women’s reported powder use from sometimes decades ago and try to identify an association between those habits and disease genesis?

One team of researchers from the National Institutes of Health chose the latter approach. In the largest study to date on the topic, published yesterday in JAMA, the group looked at more than 250,000 women who were enrolled across 4 US cohort studies and concluded there was not a “statistically significant association” between the use of powder in the genital area and ovarian cancer. 1

“We thought this was an important public health question,” said lead author Katie O’Brien, PhD, an epidemiologist at the National Institute of Environmental Health Sciences. “Previous studies that found positive associations were retrospective case-control ones. Investigators picked women who’d already been diagnosed with ovarian cancer and asked what they might have been exposed to.” said Dr O’Brien. “There’s a concern that they might answer differently after they heard of the lawsuits,” she added, referring to recent cases in several states brought against talcum powder manufacturer Johnson & Johnson by women who claim the product caused them to develop ovarian cancer. “Our strengths were the size of the study and the prospective design.”

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Yet Dr O’Brien points out that the conclusion from the study was not definitive. The depth of analysis was limited by inconsistent data from the 4 different studies, as the researchers did not uniformly ask women how long or how often they used powder or what type was used.

For example, some varieties of powder contain cornstarch, and despite the existence of an industry ban against mining talc with asbestos, it’s still occasionally found in powder samples.

Johnson & Johnson in October 2019 recalled 33,000 bottles of baby powder after asbestos was discovered in a single bottle. (The US Food and Drug Administration will hold a public meeting in February 2020 to discuss testing methods for asbestos in talc.)2 “The takeaway is that this was the largest study ever done, but it still might not be big enough to detect a small change in risk,” said Dr O’Brien. “We didn’t find anything conclusive. The association was small. We can’t measure causality, but we can’t say for sure that there is no association.”

This article originally appeared on Cancer Therapy Advisor