Experts debate breast cancer study

ORLANDO, Fla. — A new study seems to suggest that low-fat diets can help prevent a return of breast cancer in certain women, but many specialists disagreed with the conclusions, saying other factors might have played a role.

The report created a buzz at the world's largest cancer meeting, the American Society of Clinical Oncology, where it was presented on Monday and immediately made headlines on television and the Internet.

Many previous studies have failed to find that cutting fat in the diet can prevent breast cancer, so some doctors urged caution in interpreting 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 other 975 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 to 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 posted on its Web site Monday.