Among patients with early stage breast cancer who reduced their dietary fat intake for 5 years following a diagnosis, after more than 15 years follow-up, death rates from all causes were significantly reduced in those who had hormone-unrelated breast cancer, according to data from the Women’s Intervention Nutrition Study (WINS) presented at the 2014 San Antonio Breast Cancer Symposium.

“The current findings with respect to long-term influence of dietary lifestyle intervention on overall survival are mixed, but of potential importance,” said Rowan Chlebowski, MD, PhD, medical oncologist at the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center.

“In a prior report of WINS after 5 years follow-up, relapse events were 24% lower in the intervention group. In the current report, the intervention influence on long-term survival was examined,” Chlebowski continued. “Overall, while the death rate was somewhat lower in the intervention group compared with control group (13.6% vs 17%, respectively), the difference was not statistically significant. However, in exploratory subgroup analyses, in women with estrogen receptor [ER]-negative cancers, a 36%, statistically significant reduction in deaths was seen in women in the intervention group,” said Chlebowski.

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The reduction was even more significant, at 56%, for women with cancers that were both ER- and progesterone receptor [PR]-negative, Chlebowski added.

“HER2 evaluation was not available when this study was conducted, but it is likely that a substantial number of ER/PR-negative breast cancers were also negative for HER2, making them triple-negative breast cancers, which generally have a poor prognosis,” Chlebowski said. “The signal that perhaps a lifestyle intervention targeting dietary fat intake associated with weight loss could substantially increase the chances of survival for a woman with triple-negative breast cancer could influence this group of patients.”

“The dietary intervention was supported for a median of 5 years. Our findings suggest that if a lifestyle intervention is to have long-term influence on clinical outcome, it must be a lifelong change rather than be a short-term alteration,” Chlebowski said.

The WINS was a randomized trial, to which the investigators recruited 2,437 women ages 48 to 79 years with early stage breast cancer receiving standard-of-care treatments at 39 centers in the United States. Of them, 1,597 had ER-positive breast cancer, 478 had ER-negative breast cancer, and 362 had ER/PR-negative breast cancer. Within 6 months from diagnosis, all women were randomly assigned either to a dietary intervention group or to a control group.

The goal of dietary intervention was to lower fat intake for 5 years while maintaining nutritional adequacy. Centrally trained registered dieticians implementing a low-fat eating plan gave women in the intervention group a fat gram goal, explained Chlebowski.

The women underwent eight biweekly individual counseling sessions with subsequent contacts every 3 months. The women monitored their own fat/gram intake using a keeping score book. Fat intake was externally monitored by unannounced 24-hour telephone recalls performed annually.

After 5 years of dietary intervention, fat calories were lowered by 9.2% and body weight was lowered by nearly 6 pounds in the intervention group, compared with the control group.

This study was funded by the National Cancer Institute and the American Institute of Cancer Research. Chlebowski has received consulting support from Pfizer, Novartis, Amgen, Genomic Health, and Novo Nordisk, and honorarium from Novartis.