"Using talcum powder does NOT raise the risk of ovarian cancer as study of 250,000 women debunks fears after decades of uncertainty," reports the Mail Online.
Some women use talcum powder on their vulva (external genital area). The practice has been linked to ovarian cancer, with high-profile lawsuits in the US against manufacturer Johnson & Johnson.
The studies leading to these lawsuits may have been flawed, because they relied on women with and without cancer being asked to remember if they had used talc on their vulva. Women with cancer are more likely to remember or mention something that could be linked to cancer than women without, meaning these studies could have biased results.
A new review, which prompted the Mail's headline, combined information from 4 large studies that asked women a range of questions – including about talc use – and then followed them up for an average of 11 years. This study found that women who used talc were no more likely to have developed ovarian cancer than those who did not use it.
The study is reassuring, although the researchers point out that as ovarian cancer is quite rare, they cannot rule out a very small increase in risk even with a large study.
There is no need to use talc on the vulva for hygiene reasons.
Where did the story come from?
The researchers who carried out the study were from the National Institute of Environmental Health Sciences, the H Lee Moffitt Cancer Center and Research Institute, the Fred Hutchinson Cancer Research Center, National Cancer Institute, University of Florida College of Medicine, Social and the company Scientific Systems Inc, all in the US. The study was funded by the US National Institutes of Health and the National Cancer Institute. It was published in the peer-reviewed Journal of the American Medical Association.
The study was widely reported in the UK media, with most reports speculating that the study would lead to the reversal of lawsuits compelling Johnson & Johnson to pay millions of dollars in compensation to women who claim talc caused their ovarian cancer.
Only a few reports, including The Independent, make clear that the study did not rule out a small increase in risk.
What kind of research was this?
This was a meta-analysis of 4 cohort studies. It is unclear whether the studies were selected by systematic review, although the authors say that "it is believed that no other large prospective cohorts have collected data" on the topic.
Cohort studies are good ways to look for links between risk factors (in this case talc use) and outcomes (ovarian cancer) but they cannot tell us whether a risk factor is a direct cause of the outcome.
What did the research involve?
Researchers combined data from 4 cohort studies of US women, who were asked about their use of powder (including talc) in the genital area. The women were followed up to see if they developed cancer. The studies started in 1976, 1989, 1993 and 2003, and women were asked about their use of talc in different ways, with varying timescales and frequencies of use.
The researchers did not use data from women who had ovarian cancer at the start of the study, or who had no data about talc use or ovarian cancer. The studies included data about women's health and lifestyles. The researchers adjusted their figures to take account of the following potential confounding factors:
- age and ethnic background
- body mass index (BMI)
- whether they had children
- whether they smoked
- oral contraceptive or hormone replacement use
- whether they had a hysterectomy or operation to tie off their fallopian tubes
- whether they had gone through the menopause
What were the basic results?
The 252,745 eligible women in the studies were followed up for an average 11.2 years. Of these women, 38% said they had used talc on their vulva and 2,168 women developed ovarian cancer. That represents 58 cases for every 100,000 women per year.
The researchers said that, after accounting for confounding factors, women who used talc were not more likely to develop ovarian cancer than women who did not use talc.
The results showed that the risk of ovarian cancer for women who used talc was between 1% lower and 17% higher than those who had never used talc (hazard ratio 1.08, 95% confidence interval 0.99 to 1.17). While that means we cannot be sure that there is not a small increased risk, the difference is small enough that it could have come about by chance.
The figures were similar when researchers compared women who used talc weekly, or had used talc for more than 20 years. Any differences in the results between the groups of women were small enough to have come about by chance.
How did the researchers interpret the results?
The researchers say that "there was not a statistically significant association between self-reported use of powder in the genital area and incident ovarian cancer [diagnoses of ovarian cancer]". They go on to say "the study may have been underpowered to identify a small increase in risk". This means that, although the study was large, it was arguably not large enough in statistical terms for the researchers to be entirely sure there was not a very small increase risk of ovarian cancer associated with the use of talc.
For women who may have worried that use of talc on their vulva has put them at increased risk of ovarian cancer, this study should provide reassurance. Although a small increase in risk cannot be ruled out altogether, any increase is likely to be very small as it was not enough to show up in this study. So any adverse effect on a wider population level, if it does actually exist, is likely to be tiny.
The study has some limitations. Because the studies included varied in how they asked women about talc use, the figures for length of use or frequency of use are less reliable. The study could not look at type of powder used, or assess whether use at a particular age was linked with increased risk. The women in the study were mostly white and well-educated and the results may not apply to other groups of women.
There is no particular need to use talc or any other product on the vulva for hygiene reasons, however. Washing with water is sufficient, and use of scented products can cause irritation to sensitive skin.
The main risk factors for ovarian cancer are increasing age, having a condition that affects the womb such as endometriosis and inheriting a faulty gene. Other factors may include being overweight or obese, and smoking.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Mail Online, 7 January 2020
The Daily Telegraph, 7 January 2020
The Sun, 7 January 2020
The Times (subscription required), 8 January 2020
Links to the science
JAMA Oncology. Published online 7 January 2020