Study Links Obesity to Ovarian Cancer

By RONI CARYN RABIN
The New York Times
Published: Jan 13, 2009

Obese older women who never took postmenopausal hormones are at almost double the risk of developing ovarian cancer compared to their normal weight peers, a new study finds.

Among all older women, however, obese women were only at slightly higher risk for ovarian cancer than those of normal weight, the scientists found.

Researchers at the National Cancer Institute looked at differences among women who had never used hormone replacement therapy because it may play a role in the development of cancer. The comparison helps to tease out the effects of other risk factors, the authors said.

The study is to be published in the Feb. 15 issue of the journal Cancer.

The findings add to an ongoing scientific controversy over the potential association between body weight and ovarian cancer. “We speculate that what may be driving the increased risk among the obese is the surplus estrogen produced by the fat cells in the body,” said Dr. Michael F. Leitzmann, a former investigator at the National Cancer Institute and first author of the paper.

The epidemiological study looked at 94,525 women ages 50 to 71. Over a seven-year period, 303 of the women developed ovarian cancer. Overall, women who were obese, defined as having a body mass index of 30 or more, were 1.26 times more likely to have developed the cancer than those of normal weight, defined as having a B.M.I. under 25. That was a statistically insignificant difference, the researchers said.

But in a subgroup of women who had never used hormone replacement therapy, obese women were 1.83 times more likely to have developed the cancer than women of normal weight.

Among those who had taken hormones, there was no association between B.M.I. and ovarian cancer, the study found. B.M.I. was also not found to play a role in ovarian cancer risk for women with a family history of the disease.

Oral contraceptive use and having had children are associated with a decreased risk of ovarian cancer, while a family history of the disease and hormone therapy use are associated with an increased risk.

Earlier studies exploring the link between obesity and ovarian cancer have been inconsistent and contradictory, experts said, and this finding likely is not the last word on the matter.

A 2007 review of earlier clinical trials, called a meta-analysis, concluded that being overweight in adulthood was associated with a 16 percent increase in the risk of ovarian cancer, while being obese as an adult was linked to a 30 percent increase. But a pooled analysis published last year found that B.M.I. was tied to increased odds of ovarian cancer only in premenopausal women, who are at very low risk to begin with.

Leo Schouten, an author of the pooled analysis, noted in an e-mail message that questions about the association will linger. “This needs to be replicated in other populations (with lower proportions of postmenopausal hormone users) before we can decide whether this is a real and not a chance finding,” he said.

James V. Lacey Jr., an author of the new study, said that the earlier meta-analyses had included older data, yet more Americans are obese now and different disease risks may be emerging.

“It’s another piece of the puzzle,” he said.

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