The Women’s Intervention Nutrition Study (WINS) presented on Friday at the 2014 San Antonio Breast Cancer Symposium (Abstract S5-08) found that, on average, women who reduced their dietary fat intake through low-fat diets following an early-stage breast cancer diagnosis were not more likely to survive their breast cancer than women who did not modify their diet. The randomized study was launched in the 1990s and enrolled 2,437 mostly-post menopausal women between ages of 48 and 79.
Researchers looked at the effects of fat reduction (rather than weight loss) in the diets of women diagnosed with breast cancer in an effort to study whether low fat diets are beneficial for survival outcomes of non-metastatic breast cancer. [Although weight loss was not a target, on average women in the low fat group lost approximately six pounds, maintained through the five year study.] Funding and intervention ended in 2004 but researchers have been able to follow up using death registry through 2013.
Despite the fact that the study found no statistically significant difference in death rates between women who followed a low fat diet for five years after their breast cancer diagnosis compared to those who did not reduce dietary fat intake (13.6% vs. 17%), a sub-set analysis found that a low fat diet reduced mortality for women with cancers that were not hormone driven. Because the study was initiated twenty years ago in the early 1990s, HER2 status and treatment was not available.
Women with ER–negative cancers who followed a low fat diet experienced a 36% statistically significant reduction in deaths. The benefit was even more significant, at 56% for women with cancers that were both ER- and PR-negative tumors. Another way to look at this is women with hormone negative cancers who followed a low fat diet for five years lived on average 1.9 years longer than women who did not make changes to their diet.
Maximal effect of the low fat diet for women with ER–negative cancers was found to be up to ten years: for some women with hormone negative cancers who benefit from a low fat diet, five years of dietary fat reduction (reducing fat from about 30% of diet to 20%), can produce a lingering survival benefit up to 10 years later.
“Final survival analysis from the randomized Women’s Intervention Nutrition Study (WINS) evaluating dietary intervention as adjuvant breast cancer therapy”. Program shows Rowan Chlebowski, MD, PhD, medical oncologist at the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center, presented the data.