Decreased Fat Intake May Improve Survival in Some Breast Cancers

Long-term follow-up of the Women’s Intervention Nutrition Study (WINS) indicated that although a reduction in dietary fat intake for 5 years did not improve survival in the overall population of women with breast cancer enrolled in the trial, reductions in death rates were seen for those women with estrogen receptor (ER)- and progesterone receptor (PR)-negative disease.

Rowan Chlebowski, MD, PhD, medical oncologist at the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center, presented the data taken from more than 15 years of follow-up at the 2014 San Antonio Breast Cancer Symposium (SABCS).

The study showed that women with ER- and PR-negative disease assigned to the dietary intervention had a 56% reduced risk for death compared with those assigned to the control group.

The WINS study was started in 1994 when it was believed that dietary fat intake might have been related to breast cancer outcomes. The trial included 2,437 women aged 48 to 79 years. Of them, 1,597 had ER-positive breast cancer, 478 had ER-negative breast cancer, and 362 had ER/PR-negative breast cancer.

The women were randomly assigned in a 60/40 fashion to a dietary intervention or the control group. The intervention consisted of eight one-on-one visits with a registered dietitian who had been trained on a low-fat eating plan. Women were enrolled from 1994 to 2001 and the intervention ended in 2004. Women were followed for death until 2013.

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

The researchers had previously reported that relapse-free survival was reduced by 23% in the dietary intervention group (HR = 0.76; 95% CI, 0.60-0.98).

Overall survival analysis showed that although the mortality rate was numerically lower in patients assigned to the dietary intervention, there was no significant difference between the two study arms (17% for the intervention vs 13.6%).

However, when the researchers looked at outcomes in women with ER-negative disease they found that these women assigned the intervention had a 36% improvement in overall survival (HR = 0.64; 95% CI, 0.41-0.99), with a 1.9-year improvement in median survival compared with control patients (11.7 years vs 13.6 years).

When they looked at women with both ER- and PR-negative disease, the researchers found that women assigned the intervention had a 54% improvement in overall survival, with a median 2.3-year increase in median survival (11.7 years vs 14 years).

“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 in a prepared statement. “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.”

Commenting on the results of the study, C. Kent Osborne, MD, director of the Dan L. Duncan Cancer Center at Baylor College of Medicine, said, “When I look at these results they are pretty remarkable in the ER-negative subset, showing results reducing risk for death that are as good or greater than what we see with our best treatment.”

Reference

1. Chlebowski RT, Blackburn GL, et al. Final survival analysis from the randomized Women's Intervention Nutrition Study (WINS) evaluating dietary intervention as adjuvant breast cancer therapy. Presented at 2014 San Antonio Breast Cancer Symposium; December 9-13, 2014; San Antonio, Texas. Abstract S5-08.