San Antonio, TX—Results of a new nutrition study show that women who reduced their intake of dietary fat for 5 years after being diagnosed with early breast cancer had significantly lower rates of death from all causes compared with controls, at 15 years of follow-up; this reduction was seen specifically in women with hormone receptor (HR)-negative breast cancer. No long-term effect of dietary fat reduction on mortality was observed in women with HR-positive breast cancer. The results of the study, called Women’s Intervention Nutrition Study (WINS), were presented at the 2014 San Antonio Breast Cancer Symposium.
“These findings with respect to long-term influence of dietary lifestyle intervention on overall survival are mixed, but of potential importance,” said lead investigator Rowan T. Chlebowski, MD, PhD, of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA.
At 15 years, the overall death rate was lower in the dietary intervention group than in the control group—13.6% versus 17%, respectively—in the overall analysis, but this difference did not reach statistical significance. An exploratory analysis showed a 36% reduction in death rate in women with estrogen receptor (ER)-negative breast cancer who lowered their dietary fat intake.
The WINS Details
The WINS trial enrolled 2437 women with early breast cancer who were treated at 39 centers in the United States with standard of care; the patients’ ages at enrollment ranged from 48 to 79 years.
Of this group, 1597 patients had ER-positive breast cancer, 478 had ER-negative breast cancer, and 362 had ER-negative/progesterone receptor (PR)-negative breast cancer. Within the first 6 months after diagnosis, women were randomized to a dietary fat intervention or to the control group.
The dietary intervention group had 975 patients; of these, 205 women had ER-negative, and 147 had ER-negative and PR-negative (ie, double-negative) breast cancer. The control group included 1462 women; of these, 273 had ER-negative, and 215 had ER-negative/PR-negative breast cancer.
In the intervention group, centrally trained dietitians counseled women for 8 biweekly individual sessions on how to implement a low-fat diet, and then the women were contacted by the dietitians every 3 months for 5 years. Women assigned to the dietary intervention group kept diaries of their fat intake (noted in grams).
At 5 years, fat calories were 9.2% lower in the intervention group, and these women lost approximately 6 pounds on average compared with the control group.
Dr Chlebowski noted that although HER2 status was not assessed at the time of the study, he suggested that women with triple-negative breast cancer (ER-negative, PR-negative, and HER2-negative status) might also benefit from dietary fat reduction based on these results. He added that lowering dietary fat is a good strategy for overall health, but this study highlights specific benefits in this patient population.