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Original Investigation
October 11, 2018

Association of Low-Fat Dietary Pattern With Breast Cancer Overall Survival: A Secondary Analysis of the Women’s Health Initiative Randomized Clinical Trial

Author Affiliations
  • 1City of Hope National Medical Center, Department of Medical Oncology and Therapeutics Research, Duarte, California
  • 2Fred Hutchinson Cancer Research Center, Division of Public Health Sciences, Seattle, Washington
  • 3Wayne State University, Karmanos Cancer Institute, Detroit, Michigan
  • 4Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts
  • 5Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Department of Medicine, Torrance, California
  • 6Stanford Prevention Research Center, School of Medicine, Stanford University, Palo Alto, California
  • 7Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York
  • 8Stony Brook University, Preventive Medicine, Stony Brook, New York
  • 9Department of Public Health Sciences, University of California at Davis
  • 10College of Public Health, University of Iowa, Iowa City/Davenport
JAMA Oncol. 2018;4(10):e181212. doi:10.1001/jamaoncol.2018.1212
Key Points

Question  Is implementation of a low-fat eating pattern associated with breast cancer outcome?

Finding  In this secondary analysis of the Women’s Health Initiative randomized clinical trial that included 1764 postmenopausal women who received a diagnosis of breast cancer during the dietary intervention period, those randomized to a low-fat dietary pattern had increased breast cancer overall survival.

Meaning  A dietary change may be able to influence breast cancer outcome.

Abstract

Importance  In a randomized clinical trial, a low-fat eating pattern was associated with lower risk of death after breast cancer. However, the extent to which results were driven by dietary influence on survival after breast cancer diagnosis was unknown.

Objective  To determine the association of a low-fat dietary pattern with breast cancer overall survival (breast cancer followed by death from any cause measured from cancer diagnosis).

Design, Setting, and Participants  This is a secondary analysis of the Women’s Health Initiative randomized clinical trial that was conducted at 40 US clinical centers enrolling participants from 1993 through 1998. Participants were 48 835 postmenopausal women with no previous breast cancer and dietary fat intake of greater than 32% by food frequency questionnaire.

Interventions  Participants were randomized to a dietary intervention group (40%; n = 19 541) with goals to reduce fat intake to 20% of energy and increase fruit, vegetable, and grain intake or a usual-diet comparison group (60%; n = 29 294). Dietary group participants with incident breast cancers continued to participate in subsequent dietary intervention activities.

Main Outcomes and Measures  Breast cancer overall survival for incident breast cancers diagnosed during the 8.5-year (median) dietary intervention, examined in post hoc analyses after 11.5 years (median) postdiagnosis follow-up.

Results  Of 1764 women diagnosed with breast cancer during the dietary intervention period, mean (SD) age at screening was 62.7 (6.7) years and age at diagnosis was 67.6 (6.9) years. With 516 total deaths, breast cancer overall survival was significantly greater for women in the dietary intervention group than in the usual-diet comparison group (10-year survival of 82% and 78%, respectively; hazard ratio [HR], 0.78; 95% CI, 0.65-0.94; P = .01). In the dietary group there were fewer deaths from breast cancer (68 vs 120; HR, 0.86; 95% CI, 0.64-1.17), other cancers (36 vs 65; HR, 0.76; 95% CI, 0.50-1.17), and cardiovascular disease (27 vs 64; HR, 0.62; 95% CI, 0.39-0.99).

Conclusions and Relevance  In women who received a diagnosis of breast cancer during the dietary intervention period, those in the dietary group had increased overall survival. The increase is due, in part, to better survival from several causes of death.

Trial Registration  ClinicalTrials.gov Identifier: NCT00000611

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