Among early-stage breast cancer patients who reduced their dietary fat intake for five years following a diagnosis, after over 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 Centre.
“In a prior report of WINS after five years follow-up, relapse events were 24 percent 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 percent versus 17 percent, respectively), the difference was not statistically significant. However, in exploratory subgroup analyses, in women with estrogen receptor [ER]-negative cancers, a 36 percent, statistically significant reduction in deaths was seen in women in the intervention group,” said Chlebowski.
The reduction was even more significant, at 56 percent, 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 five 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 randomised 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 centres 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 six months from diagnosis, all women were randomly assigned either to a dietary intervention group (975 patients, of whom 205 had ER- negative cancer, and 147 had ER/PR-negative cancer) or to a control group (1,462 patients, of whom 273 had ER-negative cancer, and 215 had ER/PR-negative cancer).
The goal of dietary intervention was to lower fat intake for five years while maintaining nutritional adequacy.
Women in the intervention group were given a fat gram goal by centrally trained, registered dieticians implementing a low-fat eating plan, explained Chlebowski.
The women underwent eight biweekly individual counselling sessions with subsequent contacts every three months.
The women self-monitored their fat/gram intake using a “keeping score” book. Fat intake was externally monitored by unannounced 24-hour telephone recalls performed annually.
After five years of dietary intervention, fat calories were lowered by 9.2 percent and body weight was lowered by nearly 6 pounds in the intervention group, compared with the control group.