The largest study to date, published in the Journal of the American Medical Association (JAMA) found no significant association between ovarian cancer and the use of powder-based products in the vaginal area.

There is widespread apprehension that there is a link between the use of talcum powder in genital area and ovarian cancer. The news story got extensive coverage in the media.

A study carried out by a team led by Dr. Katie O’Brien from the NIH's National Institute of Environmental Health Sciences and the National Cancer Institute and published online on January 7, 2020 in the journal JAMA covered a quarter-million women from four U.S. cohorts. The researchers grouped the users into four categories, never, ever, frequent – at least once a week for 10 to 13 years and long-term- for more than 13 years. Subjects had a median age of 57 years with a median follow up period of 11.7 years.

The exposure data on use of powder in the genital area from each cohort and the frequency of use depended on how the researchers gathered them. Some women applied powder to their genitals, either through direct application or on underwear, sanitary napkins, diaphragms or tampons.

In an accompanying editorial in the same issue of the journal, Dr. Dana R. Gossett, Department of Obstetrics, Gynaecology and Reproductive Sciences, University of California, San Francisco and Dr. Marcela G. del Carmen, Department of Obstetrics, Gynaecology, and Reproductive Biology, Harvard University Medical School, Boston, noted that investigations of an association between the use of talc-containing powders for genital hygiene and epithelial ovarian cancer risks have provided inconsistent results to date and resulted in ongoing controversy.

"Since 1971, peer-reviewed articles have documented the possible association between talc use and the development of ovarian cancer,” they clarified.

“However, a PubMed search covering the last 5 decades identified only 17 primary or secondary studies and 36 other articles that were reviews, commentaries, meta analyses, or letters to the editor. In short, while some investigations have been reported, the majority of publications were opinion and discussion articles,” they added.

According to the editorial, the study by O’Brien et al. represents the largest cohort to date to examine whether an association exists between powder use in the genital area and ovarian cancer risk, and the findings are overall reassuring.

“Yet, despite 3.8 million person-years of observation in the study population, the number of Ovarian cancer cases was small, and it is possible that the study was underpowered to detect small increases or decreases in ovarian cancer rates," they cautioned.

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The researchers listed the limitations of the study and cautioned that the data had notable shortcomings.

The study that included cohorts varied widely in how they assessed exposure, particularly the duration and frequency of powder use; there was no evidence of between-study heterogeneity for either the pooled or meta-analysis models of 'ever use' vs 'never use', but because the two largest studies were missing information on duration and frequency of powder use, the dose-response analyses are underpowered compared with the main results and thus difficult to interpret.

They conceded that the study may have limited generalizability.

“All 4 cohorts included predominately white, well-educated women, approximately half of whom had a BMI of less than 25, which could raise concerns about generalizability, especially since these factors may be related to powder use. However, these studies have high retention rates and accurate self-reported data, increasing internal validity,” they clarified.

“In this analysis of pooled data from women in 4 US cohorts, there was not a statistically significant association between self reported use of powder in the genital area and incident ovarian cancer. However, the study may have been underpowered to identify a small increase in risk,”  Dr Katie M. O’Brien and her colleagues concluded finally.

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In a press release from the Science Media Centre, UK, Prof Iain McNeish, Director of the Ovarian Cancer Action Research Centre at Imperial College, London, said:

“This is a very well-conducted study by a highly respected group of researchers. Proving causation links of this type is incredibly difficult and the authors are very careful to highlight the potential limitations of their study. However, this research is robust, analysing data from 250,000 women followed for an average of over 11 years, and has concluded there is no statistically significant relationship between talc use and the development of ovarian cancer.”

Prof. Justin Stebbing, NIHR Research Professor of Cancer Medicine and Medical Oncology, Imperial College London, noted that the study is a very well-conducted rigorous investigation with pooled results from 4 studies in over 250,000 women, to show that talcum powder didn’t cause ovarian cancer.

“There weren’t many cases of ovarian cancer in the group so it’s possible a small effect has been missed, but it doesn’t look like talc is a carcinogen which is an important and reassuring finding, especially as they also looked at duration and frequency of use, again finding no causative effects,” he reassured the public.

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The WHO’s International Agency for Research on Cancer (IARC) concluded that there is only 'possible' evidence that perineal use of talc-based body powder may be carcinogenic.

According to Prof. Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, ‘possibly carcinogenic’, is the weakest classification that actually comes down on the side of something possibly being able to cause cancer, means that they felt the evidence is not very clear.

In Dr. Dinerstein’s opinion, the higher hazard ratio for women using talc and having patent reproductive tracts certainly bears further scrutiny.

He quoted the editorial in the journal to highlight an important dilemma:

"Women with intact reproductive tracts who used powder in the perineal area developed ovarian cancer more frequently than non users is below the effect size that epidemiologists generally consider important and should not be selectively highlighted by the statistically unsophisticated reader as evidence of a relationship."

According to Dr Dinerstein, “The courts, and juries, are statistically unsophisticated. Understanding scientific evidence is frequently a victim in court, so the impact of this study may be negligible.”

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Where does this new study leave Johnson and Johnson? Presently, the company is fighting a litigation in which a jury in the US state of Missouri awarded Johnson & Johnson $4.7 bn (£3.6 bn) in damages to 22 women who alleged that the company’s talc products caused them to develop ovarian cancer. The company is facing 15,500 law suits related to products containing talc. The New York Times (Oct 4, 2019) reported that J&J successfully defended some lawsuits, and it’s appealing nearly all of the 14 cases it has lost, including a nearly $4.7 billion judgment last year.

On December 23, 2019, The Kansas City Star reported that a St. Louis jury has ruled in favor of Johnson & Johnson in the latest of several lawsuits alleging that the company’s baby powder caused ovarian cancer. The lawsuit is among several filed on behalf of thousands of women who claim Johnson & Johnson's talcum powder contributed to their ovarian cancer.

On January 6, 2020 (The Los Angeles Times), J&J resolved a woman’s claims that asbestos-laced baby powder caused her cancer before a California jury got a chance to consider the allegations in one of dozens of cases to go to trial.

In Dec 2019, J&J scored a big win in a talc case in St. Louis, where in 2018 it was hit with a $4.7-billion verdict on behalf of more than 20 women blaming their cancers on its baby powder. In the December case, jurors rejected a woman’s claim that her ovarian cancer was tied to use of J&J’s talc-based powder.

The impact the JAMA study will have on these cases is not predictable!

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

Dr K S Parthasarathy is a freelance science journalist and a former Secretary of the Atomic Energy Regulatory Board. He is available at ksparth@yahoo.co.uk