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Washington (AFP)
It is sometimes the lack of results that is the most interesting result. A synthesis of studies published Tuesday and involving 250,000 women in the United States did not find a statistical link between the use of talc on the genitals and the risk of ovarian cancer.
Fewer and fewer women do this, but four in ten participants have used talc to absorb moisture and odors, either by direct application to the genitals, or by putting it on undergarments, a sanitary pad or a diaphragm. It is mainly the older generations that do this.
In the 1970s, concern arose about the contamination of talc with asbestos, which is often similar in nature to the minerals used to make talc. Then studies showed a higher risk of ovarian cancer in talc users, who were suspected of being able to go up to the ovaries via the vagina and the uterus. Lawsuits have been launched against the giant Johnson & Johnson.
But there was a doubt about the reality of this link, since the number of studies conducted has been low in five decades, with statistically inconclusive results.
The effect is difficult to isolate because ovarian cancers are rare: 1.3% of women are at risk of developing it in their lifetime.
Researchers from various research centers in the United States, funded by the National Institutes of Health (NIH), therefore produced a synthesis of four large cohort studies that followed a quarter of a million women in the United States from 1982 to 2017. These studies ask participants every one or two years about various health issues, including the use of talc or powder.
The hope, by increasing the size of the sample of participants, is to be able to detect with statistical validity weak effects which, on a smaller population, would not be detectable.
– Rigorous study –
In total, of these 250,000 women followed for a median of 11 years, approximately 2,200 ovarian cancers have been reported.
The important finding is that no statistical difference was observed between women who reported using talc and those who never used talc. Ditto when comparing the frequency or duration of use.
“There is no significant statistical association between the reported use of talc on the genitals and the risk of ovarian cancer,” write the authors of the analysis, published in the journal Jama.
“This is a well-conducted study,” said Iain McNeish, director of the ovarian cancer research center at Imperial College London.
As always in observational studies, it is not possible to conclude on causality, only on the absence or presence of statistical links. “There remains uncertainty about the existence of such an association,” wrote Kevin McConway, professor of applied statistics at The Open University. If the link between talc and cancer really existed, he adds, “the increase in risk would probably be small”.
The synthesis released on Tuesday is the largest analysis ever on the subject to date, and it will likely not be possible to do better in the future as fewer women use talc, experts say in a published editorial. by Jama.
In the United States, the Johnson & Johnson group has defended itself for years against thousands of complaints against its talcated products, accused of being carcinogenic. He was, for example, sentenced in 2018 to pay $ 4.7 billion to 22 women, a verdict challenged on appeal. In October, the company recalled a batch of baby talcum powder after health inspections discovered traces of asbestos.
© 2020 AFP
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