Diet does not improve breast cancer survival

NEW YORK (Reuters Health) - Among breast cancer survivors, adopting a low-fat diet high in vegetables, fruit and fiber does not prevent the cancer from returning or prolong survival, according to a paper in the Journal of the American Medical Association.

Dr. John P. Pierce and his associates designed the Women’s Healthy Eating and Living (WHEL) trial, based on evidence that plant-derived foods contain anti-cancer chemicals.

Pierce, at the University of California, San Diego, and his team describe the intervention as “a telephone counseling program supplemented with cooking classes and newsletters that promoted daily targets of 5 vegetable servings plus 16 ounces of vegetable juice; 3 fruit servings; 30 grams of fiber; and 15 to 20 percent of” calories from fat.

Subjects in the comparison group received care as usual and were given publications from the National Cancer Institute and the US Department of Health and Human Services, describing the “5-A-Day” dietary guidelines. In addition to five servings of vegetables and fruits, the diet recommends 20 grams of fiber and less than 30 percent of calories from fat.

Between 1995 and 2000, WHEL investigators enrolled more than 3,000 women who were previously treated for breast cancer. Follow-up continued until 2006. They report outcomes for 1,537 subjects randomly assigned to the intervention group and 1,561 assigned to the comparison group.

As noted, the special diet did not prevent breast cancer from returning and it did not improve survival. Roughly 17 percent of patients in each group had their cancer return and about 10 percent in each died during follow-up.

In a related editorial, Dr. Susan M. Gapstur and Dr. Seema Khan, from the Feinberg School of Medicine in Chicago, compared the WHEL study findings with those of the Women’s Intervention Nutrition Study (WINS). According to WINS trial results, a low-fat diet imparted significant increases in cancer-free survival, which was associated with a 6-pound weight difference between study groups at year 3.

In the WHEL study, on the other hand, weight loss and amount of daily calories did not differ between the two patient groups, and the actual percentage of calories from fat increased during the trial in both groups.

The editorialists suggest that “these results call into question the validity of some components of the self-reported dietary data,” and they attribute the negative findings at least partially to lack of adherence to the diet.

SOURCE: Journal of the American Medical Association, July 18, 2007.