Low fat diet helps postmenopausal women avoid deadly breast cancers

Women who stayed on a low fat diet for approximately eight years reduced their risk of death from invasive breast cancers and improved their survival rates when compared with women who had not followed the dietary regimen, according to a study presented at a clinical trial plenary session, entitled "Transformative Clinical Trials in Breast Cancer," at the American Association for Cancer Research (AACR) annual meeting.

An association between dietary fat intake and breast cancer outcomes was suggested nearly a half-century ago but observational findings have been inconclusive. In order to determine the effects of a low fat dietary pattern on breast cancer, Rowan Chlebowski MD, PhD, of the Los Angeles Biomedical Research Institute and colleagues from the Women's Health Initiative conducted additional analyses of a randomized clinical trial that had followed 48,835 postmenopausal women.

The women were age 50-79, had no prior breast cancer, had normal mammograms and normal dietary fat intake. Of those, 19,541 women were put on a low fat diet with nutritionist-led group sessions that sought to reduce fat intake reduction to 20% of energy and increase the consumption of fruits, vegetables and grain. The other 29,294 women in the trial followed their usual dietary patterns.

After approximately eight years of remaining on the low fat diet, 1,767 of the women were diagnosed with breast cancer. Researchers found the breast cancer overall survival from diagnosis was higher in the dietary group: 82% versus 78%. The researchers said this reduction is due, in part, to better survival following breast cancer diagnosis.

"This was the first time we had examined the deaths after breast cancer among this group, and we found that a sustained low fat diet increased the survival rates among postmenopausal women after a breast cancer diagnosis," said Dr. Chlebowski, who presented the findings at the conference. "The study also suggests that women would need to remain on the low fat diets to maintain the benefits of the dietary intervention."

The researchers also reported that most breast cancer characteristics—including size, nodal status, and distribution of poor prognosis, triple negative cancers and HER2 positive cancers—were similar between the two groups of women. But there were fewer progesterone receptor negative cancers in the dietary group (28.4% versus 33%). In addition, researchers noted lower cardiovascular disease mortality in the dietary group.

At the conference in New Orleans, AACR also honored Dr. Chlebowski and 12 other Women's Health Initiative investigators with the AACR Science Team of the Year award for their work on breast cancer prevention.