Experts Debate Study on Fat, Breast Cancer
Experts Debate Study That Claims Low-Fat Diets Prevent Relapse of Breast Cancer
Associated Press | May 17, 2005
By MARILYNN MARCHIONE
Low-fat diets modestly helped women cut their chances of a recurrence of breast cancer, the first experiment to put this to the test concludes.
While some doctors said other factors like weight loss might be what's actually helping these women, they saw little reason not to recommend trimming fat for general good health.
"Where's the harm?" said Dr. David Johnson, a Vanderbilt-Ingram Cancer Center physician who is president of the American Society of Clinical Oncology.
The study was presented Monday at the oncology group's annual meeting and immediately created a buzz.
Many previous studies have failed to find that cutting fat in the diet can prevent breast cancer, so some doctors urged caution in interpreting the new information.
"There are more questions than answers," said Dr. Eric Winer, director of breast care at the Dana-Farber Cancer Institute in Boston, who had no role in the study. "What we don't want to happen is for every woman who's had breast cancer to panic if she's had a Big Mac."
The study was funded by the National Cancer Institute and involved 2,437 women at 37 sites around the country. All had surgery followed by standard chemotherapy drugs for early-stage breast cancer and five years of tamoxifen if their tumors were estrogen-receptor positive that is, helped to grow by estrogen.
As a group, 29 percent of their calories came from fat, already far lower than the typical American who gets up to half of calories from fat, according to what the women told doctors at the outset of the study.
Doctors told 1,462 of them to continue their normal diets. The 975 others were given intensive counseling eight personal, biweekly sessions with a dietitian at the outset and follow-ups every three months to help them cut fat and track what they ate.
The low-fat group averaged 33.3 grams of fat a day compared with 51.3 grams for the others.
Five years later, the cancer had returned in 9.8 percent of those on the low-fat diet versus 12.4 percent of those on standard diets, said Dr. Rowan Chlebowski of Los Angeles Biomedical Research Institute, who led the study. This translated to a 24 percent lower risk for the group as a whole.
However, the only women who benefited were those whose tumors were not helped to grow by estrogen. These women had 42 percent lower risk of recurrence if they ate low-fat diets, but they accounted for just 1 out of 5 women in the entire study similar to breast cancer cases in the general population.
Results for the other 4 out of 5 women in the study did not reach statistical significance, meaning they could have occurred by chance alone a point the American Cancer Society noted in a statement on its Web site Monday.
The advice to follow a low-fat diet to prevent breast cancer "is not something that can be taken generally" from this study's results, said the cancer society's deputy medical director, Dr. Len Lichtenfeld.
Others noted that women in the low-fat group lost on average 4 pounds, and that many studies have linked excess weight to excess breast cancer risk. The low-fat dieters also likely ate more fruits and vegetables and less red meat other things known to lower breast cancer risk.
"It could be any or all of those components that make up a low-fat-dietary pattern" that actually caused the benefit, said Dr. Steven Clinton, a nutrition and cancer prevention expert at Ohio State University.
"We can't separate those components out," Chlebowski admitted.
One study participant whose cancer has not returned, 76-year-old Jean Miller of Columbus, Ohio, coupled the low-fat diet with more exercise.
"I still pay attention to my fat grams," she said. But she also now walks, rides an exercise bike, uses a treadmill and even has taken up country line dancing.
Studies also suggest exercise helps prevent breast cancer.
Breast cancer is the most common non-skin cancer in American women. About 213,000 new cases and 40,870 deaths are expected in the United States this year, and about 1.15 million cases and 411,000 deaths worldwide.