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The findings did reveal an 8% increased risk among women who used the powder products, compared with women who never used them, but head researcher Katie O'Brien says this "is not a statistically significant increase."
This increase needs to be understood in context, she says. Given that the lifetime risk of developing ovarian cancer is only 1.3% in the first place (1.3%), an increase of 8% to that is "small," representing an estimated increased risk of just 0.09% by the age of 70.
"Although this is the largest study ever done, our findings are not definitive… We found a small, but non-statistically significant, risk. We cannot establish causality. If there is a true association [between talc powder use and ovarian cancer], the increase would likely be very small," says O'Brien.
"The overall conclusion [is] that there is no demonstrable statistically significant association between use of powder in the genital area and ovarian cancer risk… This is the key finding of the study," writes the team. "The risk is likely to be multifactorial"
When approached for comment, Don Dizon, director of women's cancers at Lifespan Cancer Institute in Providence, Rhode Island, pointed out that many factors can affect risk: "This is an example of the difficulties in concluding that any one factor increased the risk of ovarian cancer. The risk is likely to be multifactorial, and there are far better data to support other factors that also determine risk," he said. As examples, he referred to the protective effects of hormonal therapies, genetic risk, and familial predisposition to cancer.
In 2006, the International Agency for Research in Cancer classified the use of talc in the genital region as "possibly carcinogenic to humans." However, this is considered the weakest classification of cancer cause, which means the evidence to date is not yet clear.
The American Cancer Society also says that "findings have been mixed" and that, although there has been some suggestion of a possible increase in ovarian cancer risk, its bottom-line advice is: "until more information is available, people concerned about using talcum powder may want to avoid or limit their use of consumer products that contain it."
O'Brien, K.M. et al. (2020). Association of Powder Use in the Genital Area With Risk of Ovarian Cancer. JAMA. DOI: 10.1001/jama.2019.20079.
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