ORLANDO, FLA. — Breast cancer survivors on a low-fat diet had their rate of recurrence reduced by 24% in what may be the first phase III trial to show that a lifestyle change can protect cancer patients from relapse.
In a study with a median of 5 years of follow-up, investigator Rowan T. Chlebowski, M.D., determined the disease had recurred in 12.4% of postmenopausal women on a standard diet but only 9.8% of those on the low-fat regimen.
The protective effect was stronger in women who had estrogen receptor-negative tumors, he reported at the annual meeting of the American Society of Clinical Oncology.
Although patients with such tumors have an elevated risk of relapse, a low-fat diet reduced their risk of recurrence by 42%.
For women who had estrogen receptor-positive cancers, the benefit was a 15% drop in recurrence risk.
“Many physicians would say, how [could] a lifestyle intervention work at all?” Dr. Chlebowski, an oncologist at the Los Angeles Biomedical Research Institute in Torrance, Calif. acknowledged during a press briefing. “It seems unlikely just talking to a dietitian for eight visits [would] change anything.”
During a plenary session discussion of the findings, Eric T. Winer, M.D., called the results “tantalizing,” noting that “the magnitude of effects are similar to many widely accepted interventions.”
Begun in 1994 and stopped because the investigators ran out of funds, the Women's Intervention Nutrition Study (WINS) randomized women at 37 cancer centers within 365 days of surgery for early-stage breast cancer.
The women had an average age of 52 years, with a range of 48 to 79 years. Many also received radiation and adjuvant chemotherapy according to standard protocols.
A total of 975 postmenopausal women were assigned to the low-fat arm, with a goal of reducing fat intake to 15% of calories; they cut their average intake to 33.3 g of fat daily. These women attended eight biweekly nutrition counseling sessions, met with a nutritionist every 3 months, and had monthly group meetings. The program taught them to swap low-fat foods for high-fat foods (for example, eating cereal instead of baked goods), reduce intake of oils and margarines, and eat smaller portions of red meat.
The 1,462 women in the control group consumed an average of 51.3 g of fat per day on their standard diets; they had “dietitian contact” every 3 months, but no additional dietary intervention.
The goal of the low-fat diet was fat reduction, not weight loss, Dr. Chlebowski stressed.
Nonetheless, the women lost a statistically significant 4 pounds on average that may have confounded the results by contributing to the treatment effect.
“The weight loss is remarkable, as women with breast cancer tend to gain weight,” said Dr. Winer of Dana-Farber Cancer Institute in Boston. “Weight gain is common as individuals age.”
He cautioned that the study does not establish that a low-fat diet will protect breast cancer survivors and is, therefore, insufficient to recommend that postmenopausal women with breast cancer use dietary fat reduction to reduce the risk of recurrence.
Dr. Winer called for more research into dietary intervention, noting that the preliminary evidence suggests that a low-fat diet and/or weight loss might, indeed, lower the risk of recurrence.
Dr. Chlebowski said the investigators will continue to follow the patients. The effects would persist for women committed to making a dietary change, he predicted. “It is a sustainable intervention because you are eating different foods rather than trying to lose weight.”
In a statement issued by the American Cancer Society, deputy chief medical officer Len Lichtenfeld, M.D., said comparable findings would be cause for excitement if the trial had been a preventive chemotherapy study.
More trials are needed to determine whether large numbers of women can make and maintain such large dietary changes, he added.
“For now, a postmenopausal woman who has been diagnosed with breast cancer that is estrogen receptor negative should consider adopting a low-fat diet after speaking with her physician,” Dr. Lichtenfeld said. “Until this study has been confirmed by others, we can't say with absolute certainty that this will be beneficial for her breast cancer,” he said.