Dietary fat reduction and breast cancer outcome: Interim efficacy results from the women's intervention nutrition study

Rowan T. Chlebowski, George L. Blackburn, Cynthia A. Thomson, Daniel W. Nixon, Alice Shapiro, M. Katherine Hoy, Marc T. Goodman, Armando E. Giuliano, Njeri Karanja, Philomena McAndrew, Clifford Hudis, John Butler, Douglas Merkel, Alan Kristal, Bette Caan, Richard Michaelson, Vincent Vinciguerra, Salvatore Del Prete, Marion Winkler, Rayna HallMichael Simon, Barbara L. Winters, Robert M. Elashoff

Research output: Contribution to journalArticlepeer-review

657 Scopus citations


Background: Preclinical and observational studies suggest a relationship between dietary fat intake and breast cancer, but the association remains controversial. We carried out a randomized, prospective, multicenter clinical trial to test the effect of a dietary intervention designed to reduce fat intake in women with resected, early-stage breast cancer receiving conventional cancer management. Methods: A total of 2437 women were randomly assigned between February 1994 and January 2001 in a ratio of 40 : 60 to dietary intervention (n = 975) or control (n = 1462) groups. An interim analysis was performed after a median follow-up of 60 months when funding for the intervention ceased. Mean differences between dietary intervention and control groups in nutrient intakes and anthropometric variables were compared with t tests. Relapse-free survival was examined using Kaplan-Meier analysis, stratified log-rank tests, and Cox proportional hazards models. Statistical tests were two-sided. Results: Dietary fat intake was lower in the intervention than in the control group (fat grams/day at 12 months, 33.3 [95% confidence interval {CI} = 32.2 to 34.5] versus 51.3 [95% CI = 50.0 to 52.7], respectively; P<.001), corresponding to a statistically significant (P = .005), 6-pound lower mean body weight in the intervention group. A total of 277 relapse events (local, regional, distant, or ipsilateral breast cancer recurrence or new contralateral breast cancer) have been reported in 96 of 975 (9.8%) women in the dietary group and 181 of 1462 (12.4%) women in the control group. The hazard ratio of relapse events in the intervention group compared with the control group was 0.76 (95% CI = 0.60 to 0.98, P = .077 for stratified log rank and P = .034 for adjusted Cox model analysis). Exploratory analyses suggested a differential effect of the dietary intervention based on hormonal receptor status. Conclusions: A lifestyle intervention reducing dietary fat intake, with modest influence on body weight, may improve relapse-free survival of breast cancer patients receiving conventional cancer management. Longer, ongoing nonintervention follow-up will address original protocol design plans, which called for 3 years of follow-up after completion of recruitment.

Original languageEnglish (US)
Pages (from-to)1767-1776
Number of pages10
JournalJournal of the National Cancer Institute
Issue number24
StatePublished - Dec 20 2006

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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