Thursday, September 20, 2018

Perspective: Can talc baby powder cause cancer?

A jury has ordered Johnson & Johnson to pay what may be the largest award so far in a lawsuit tying ovarian cancer to talcum powder — $417 million in damages to a medical receptionist who developed ovarian cancer after using Johnson's Baby Powder on her perineum for decades. But the scientific question remains: Is it plausible that this medicine cabinet staple can cause cancer?

Eva Echeverria, 63, of East Los Angeles is one of thousands of women who have sued Johnson & Johnson claiming baby powder caused their disease, pointing to studies linking talc to cancer that date to 1971, when scientists in Wales discovered particles of talc embedded in ovarian and cervical tumors.

Only a few lawsuits have gone to trial, but so far most of the decisions have gone against the company. So did the juries get it right or wrong? It's not an easy question to answer.

Johnson & Johnson says its trademark Baby Powder is safe. Numerous studies, however, have linked genital talc use to ovarian cancer, including a report that among African-American women, it is linked with a 44 percent increased risk for invasive epithelial ovarian cancer. Many women use the powder on their inner thighs to prevent chafing, while others sprinkle it on their perineum, sanitary pads or underwear to stay "fresh" and dry.

The International Agency for Research on Cancer in 2006 classified talcum powder as a possible human carcinogen if used in the female genital area. But the agency, part of the World Health Organization, has also said pickled vegetables and coffee are possible carcinogens and that hot dogs cause cancer.

"There is no way we're ever going to know for certain that any exposure is necessarily causal to a disease," said Dr. Shelley Tworoger, an associate professor of medicine and epidemiology at Brigham and Women's Hospital and Harvard.

Cancer is hard to study because it develops over a long period of time and is influenced by many factors, including genes, behaviors and environmental exposures. The best we can do, Tworoger said, "is look at the preponderance of the evidence."

Talc is a naturally occurring clay mineral composed of magnesium and silicon. Known for its softness, it is used in cosmetic products like blush because it absorbs moisture and prevents caking. It is also an additive in tablets, chewing gum and some rice. It's often mined in proximity to asbestos, a known carcinogen, and manufacturers have to take steps to avoid contamination.

Scientists must rely on observational studies that can link an exposure to a disease but cannot determine a cause-and-effect relationship. In 1982, a Harvard professor, Dr. Daniel W. Cramer, and his colleagues compared 215 women with ovarian cancer and 215 healthy women who served as a control group. Compared with nonusers, women who used talcum powder were at nearly twice the risk for having ovarian cancer, and those who used it regularly on their genitals and sanitary pads were at more than three times the relative risk.

At least 10 subsequent studies echoed the results, with varying degrees of increased risk. But a small number of studies did not find a heightened risk for talc users.

When researchers pooled the results of similar studies involving nearly 20,000 women, they found powder use was associated with a 24 percent increased risk for ovarian cancer, an uncommon disease but one that is often fatal. If the finding is true, it means that for every five or six talcum powder users who develop ovarian cancer, one may be a result of talcum powder use, said Dr. Steven A. Narod, an expert in cancer genetics from Toronto.

But critics say such studies can get it wrong, because they quiz women about their risk factors after a cancer diagnosis. "A patient is looking for reasons, and wondering, Why did this happen to me?" said Dr. Larry Copeland, a gynecologic oncologist from Ohio State University Wexner Medical Center and paid expert for Johnson & Johnson. If a researcher asks a patient about talc use, he said, "The answer is going to be 'Aha, yeah — maybe that was it.' "

Copeland points to a large government-funded study, the Women's Health Initiative. Researchers asked 61,576 women at the beginning of the study whether they had ever used perineal powder and tracked their health. After 12 years, the study investigators found no relationship between powder use and cancer.

Why talc use might lead to cancer is not clear. Studies have shown that talc crystals can move up the genital-urinary tract into the peritoneal cavity, where the ovaries are. There is also a plausible mechanism, Tworoger said, because talc particles can set off inflammation, and inflammation is believed to play an important role in the development of ovarian cancer.

Since the research began showing a link between talc and cancer in the 1990s, officials have not acted to remove the powders or add warning labels. Although Johnson & Johnson's talc supplier added labels in 2006, J&J did not add them to its products, according to litigation documents.

© 2017 New York Times

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