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Questions follow breast cancer study

SAN ANTONIO, Texas - The first experiment to show that a low-fat diet could help prevent a return of breast cancer now indicates, with longer followup, that the benefit was almost exclusively to women whose tumor growth was not driven by hormones.

That could be huge - the new results suggest but cannot prove that these women might be able to cut their risk of dying by up to 66 percent with such diets.

"That's as great or better than any treatment intervention that we've given" for this type of cancer, which is notoriously hard to treat, said Dr. C. Kent Osborne of Baylor College of Medicine in Houston, who had no role in the study.

However, for women whose cancers are fueled by hormones - the vast majority of breast cancer patients - the diet change seemed to make little difference in the risk of recurrence or survival. Questions remained about whether those who did benefit truly were helped by cutting fat or by the weight loss that resulted.

"Maybe it raises as many issues as it answers," said John Milner, chief of nutrition science research for the National Cancer Institute, which paid for the first phase of the study.

Initial findings from the study were reported at a cancer conference in 2005 and will appear in this week's Journal of the National Cancer Institute. Updated results with longer follow-up on many of the original participants were presented Saturday at the San Antonio Breast Cancer Symposium.

The mixed results were a surprise because doctors had expected all women to benefit, said Dr. Rowan Chlebowski of the University of California at Los Angeles, who led the work.

Hormones might play such a strong role in some cancers that dietary changes have weak impact on future risk, experts said.

The study involved 2,437 women with early stage breast cancer, average age 58, at 39 sites around the country.

Some earlier studies did not find low-fat diets to reduce breast cancer risk. The new one's conclusion that some may benefit from substantially cutting fat "suggests that getting below a certain threshold of fat intake may be important," said Dr. JoAnn Manson, a women's health expert at Harvard-affiliated Brigham and Women's Hospital.

[Last modified December 17, 2006, 00:37:00]