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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 Hall
  • Michael Simon, Barbara L. Winters, Robert M. Elashoff

Research output: Contribution to journalArticlepeer-review

Abstract

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
Volume98
Issue number24
DOIs
StatePublished - Dec 20 2006

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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