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Reduced dietary fat intake extended survival in some women with breast cancer
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SAN ANTONIO — Women with early-stage, hormone-unrelated breast cancer who reduced dietary fat intake for 5 years following diagnosis demonstrated significantly lower risk for death from all causes, according to long-term results of a randomized phase 3 study presented at the San Antonio Breast Cancer Symposium.
The findings — revealed in an exploratory, post-hoc analyses of the Women’s Intervention Nutrition Study (WINS) — add to emerging evidence that support lifestyle interventions that promote weight loss maintenance and increased physical activity in patients with breast cancer, according to researcher Rowan Chlebowski, MD, PhD, medical oncologist at the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center.
“From a scientific standpoint, others will have to look at these results and decide whether they warrant support in a further randomized clinical trial to try to confirm some of these findings,” Chlebowski said during a press conference. “For women with breast cancer, there are health benefits associated with a 5% or 5-pound weight loss, and this is something they should consider.”
Preclinical and observational studies showed dietary fat intake may be associated with breast cancer outcome. Estrogen, linoleic acid and insulin-like growth factors represent a few potential mediating factors, according to background information provided by researchers.
The WINS trial, initiated in 1994, was designed to evaluate the influence of dietary fat reduction on RFS in patients with early-stage breast cancer who received standard care.
The study included 2,437 women aged 48 to 79 years with stage I to stage IIIA breast cancer who received standard-of-care treatment at one of 39 centers in the United States.
Eligibility criteria included primary surgery with or without radiation therapy, as well as receipt of systemic therapy, which — at the time of study initiation — was chemotherapy for women with ER-negative tumors and tamoxifen/chemotherapy for women with ER-positive tumors.
At the time of enrollment, all trial participants derived more than 20% of their calories from dietary fat intake.
The study population included 1,597 women with ER-positive breast cancer, 478 with ER-negative breast cancer, and 362 with ER-negative/PR-negative disease. Randomization occurred within 6 months of diagnosis.
Researchers randomly assigned 975 women to a dietary intervention group and 1,462 women to a control group.
The dietary intervention was intended to help women reduce fat intake for 5 years while maintaining nutritional adequacy. Those assigned to the intervention group underwent eight biweekly counseling sessions with trained registered dietitians, plus subsequent contact with dietitians every 3 months for the duration of the study period.
The women in the intervention arm received a fat gram goal and self-recorded their fat intake. Unannounced telephone recalls helped researchers externally monitor participants’ fat intake.
After 5 years, researchers determined women in the dietary intervention group reduced fat calories by an additional 9.2% compared with those in the control group, and they also lost nearly 6 pounds more than those in the control group.
Previously released results from WINS, based on the 5-year follow-up, showed a 24% reduction in relapse events in the intervention group.
Although funding for the intervention ended in May 2004, follow-up with death registry data has been completed through 2013. Maximum follow-up is 19.4 years.
Chlebowski and colleagues used the longer-term follow-up data to evaluate survival outcomes between the two groups.
Researchers reported a lower death rate in the intervention group (13.6% vs. 17%; HR=0.94; 95% CI, 0.76-1.2), but the difference was not statistically significant.
An exploratory analysis, however, showed women with ER-negative breast cancer appeared to derive a particular benefit from the dietary intervention. Among ER-negative patients, median survival was 13.6 years for those in the intervention group and 11.7 years for those in the control group (HR=0.64; 95% CI, 0.41-0.99). The difference was statistically significant.
Women who were ER- and PR-negative derived an even greater survival benefit from the intervention. Among those women, median survival was 14 years for those in the intervention group and 11.7 years for those in the control group (HR=0.46; 95% CI, 0.27-0.78).
The survival benefits observed among ER-negative and ER-/PR-negative patients peaked at 10 years after randomization, or about 5 years after the intervention ended. The benefit subsided slightly at 15 and 20 years post-randomization.
“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 a short-term alteration,” Chlebowski said.
The benefits observed in ER-/PR-negative patients are particularly intriguing, according to researchers.
Chlebowski cited an analysis of SEER data published in 2014 in Journal of the National Cancer Institute that indicated about 73% of ER-negative and PR-negative patients also have HER-2–negative disease. Women with triple-negative disease typically have a poor prognosis.
“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,” Chlebowski said.
For more information:
Chlebowski RT. Abstract #S5-08. Presented at: San Antonio Breast Cancer Symposium; Dec. 9-13, 2014; San Antonio.
Disclosure: The researchers report consultant roles with Amgen, AstraZeneca, Genentech, Novartis, NovoNordisk and Pfizer, as well as speaking roles with Novartis.
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Anees B. Chagpar, MD, MSc, MA, MPH, MBA, FRCS(C), FACS
This study offers some really exciting data demonstrating that a low-fat diet actually reduces mortality for some patients with breast cancer. Although there was not a statistically significant difference between the group who had the intervention and the group who did not, the group that did have the intervention had a 3.6% mortality reduction. If you look at subpopulations, those who were ER-/PR-negative — who may well be triple-negative — demonstrated a 56% reduction in mortality.So here we are, getting a huge mortality difference based on an intervention that is fairly simple and cheap, and it does not have any toxicities. We continue to see a lot of data about the impact of diet and exercise in patients with breast cancer, as well as in breast cancer survivors. These data are really exciting, and this should be part of the prescription we are writing for our patients: eat a low-fat diet, exercise and be healthy.
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Beverly Moy, MD, MPH
A lot of times, we’re asked, “Is there anything that I can do, doctor, that will [reduce] my chances of recurrence?” We are desperate for good lifestyle studies to show us benefits in reducing the risk for breast cancer recurrence. We know that exercise is important, and we know that minimization of alcohol is important. This study adds another potential benefit — having a low-fat diet that leads to weight loss.Particularly in our estrogen receptor-negative patients, which you worry about a little more because they are more aggressive cancers, they do not get any benefit from anti-estrogen pills. Low-fat diet, exercise and weight loss could potentially help improve recurrence rates and OS. So, this is potentially a really important study for our patients.
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