A new report adds ovarian cancer to the growing list of cancers that may be linked to being overweight, including post-menopausal breast cancer and cancers of the colon, endometrium, esophagus, gallbladder, kidney, pancreas and thyroid.
The report’s authors noted that the increased risk is modest and the association is not as strong as with some other cancers. And the report —an analysis of global research by the American Institute for Cancer Research and World Cancer Research Fund published this week — found that being tall has a stronger association with ovarian cancer than being heavy.
But unlike their height, women can do something about their weight. Given the link between excess fat and other diseases, including heart disease and diabetes, cancer researchers see the report’s finding as one more incentive to exercise and eat a healthy diet.
“The association with excess weight was not as strong as for other cancers, but it is something that is modifiable,” said Dr. Anne McTiernan, a cancer prevention researcher with Fred Hutchinson Cancer Research Center’s Public Health Division and a member of the panel of experts that reviewed studies for the report.
About 5 percent, or 1,112 of the 22,000 cases of ovarian cancer cases diagnosed each year in the United States, could be prevented by maintaining a healthy weight, the report said.
The Ovarian Cancer 2014 Report: Food, Nutrition, Physical Activity, and the Prevention of Ovarian Cancer is part of a continuously updated project that monitors and analyzes research on cancer prevention. The 2014 report analyzed 128 population studies that investigated how diet, weight, and activity link to ovarian cancer. Of these, 25 studies focused on weight.
The increased risk of ovarian cancer was seen in women with a BMI of 28.4 –which is considered overweight but not obese—and higher. More than 60 percent of U.S. women are considered to be overweight or obese.
BMI, or body mass index, is a common measure of body fatness. (You can calculate your BMI here.) According to the National Institutes of Health, a BMI between 18.5 and 24.5 is considered normal, 25-29.9 is considered overweight and over 30 is considered obese.
It didn’t surprise McTiernan that an increased risk was seen in women who, although not in the normal weight range, were short of obese. “BMI is a continuum,” she said. “[Overweight women] also have increased risk for other cancers, diabetes and for cardiovascular diseases.”
Excess fat may raise cancer risks in a number of ways. Fat secretes estrogen and other hormones, which can promote the growth of cancer cells. Obesity is associated with chronic inflammation, which also has been associated with cancer development.
Other reports also have linked height to elevated cancer risk. Like the others, this report did not find that tallness itself leads to ovarian cancer but that hormones and growth factors that promote height may also play a role in cancer.
Although it accounts for only about 3 percent of all cancers in women, ovarian cancer kills more than 14,000 women a year, more than any other cancer of the female reproductive system, according to the U.S. Centers for Disease Control. It is the eighth most common cancer and the fifth leading cause of cancer death among U.S. women, after lung and bronchus, breast, colorectal and pancreas cancers.
When ovarian cancer is found in its early stages, treatment is most effective. But often patients have no symptoms or attribute symptoms to other causes, giving ovarian cancer the reputation as a “silent killer” because it is often advanced by the time it is diagnosed. This lends urgency to the need for more research on how to screen, treat and prevent it.
“There aren’t many preventatives known for this rare but fairly deadly cancer,” said Dr. Ross Prentice, a former director of the Fred Hutch Public Health Division and a leader in the clinical-trial arm of the Women's Health Initiative — one of the largest clinical trials in postmenopausal women ever conducted. “We need to have a stronger research agenda, stronger information, so we can give more forceful and pointed advice to people about how to reduce their risk.”
In the meantime, excess body fat has been implicated in enough diseases to prompt women (and men) to “improve our diets and get up off the couch,” Prentice said.
Solid tumors, such as those of the ovaries, are the focus of Solid Tumor Translational Research, a network comprised of Fred Hutchinson Cancer Research Center, UW Medicine and Seattle Cancer Care Alliance. STTR is bridging laboratory sciences and patient care to provide the most precise treatment options for patients with solid tumor cancers.
Mary Engel is a former staff writer at Fred Hutchinson Cancer Center. Previously, she covered medicine and health policy for the Los Angeles Times, where she was part of a team that won a Pulitzer Prize for Public Service. She was also a fellow at the Knight Science Journalism Program at MIT. Follow her on Twitter @Engel140.