Dietary fat reduction and breast cancer outcome: interim efficacy results from the Women's Intervention Nutrition Study.
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.
Chlebowski
Rowan T
RT
Department of Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, 1124 West Carson St., Building J-3, Torrance, CA 90502-2064, USA. rchlebow@whi.org
Blackburn
George L
GL
Thomson
Cynthia A
CA
Nixon
Daniel W
DW
Shapiro
Alice
A
Hoy
M Katherine
MK
Goodman
Marc T
MT
Giuliano
Armando E
AE
Karanja
Njeri
N
McAndrew
Philomena
P
Hudis
Clifford
C
Butler
John
J
Merkel
Douglas
D
Kristal
Alan
A
Caan
Bette
B
Michaelson
Richard
R
Vinciguerra
Vincent
V
Del Prete
Salvatore
S
Winkler
Marion
M
Hall
Rayna
R
Simon
Michael
M
Winters
Barbara L
BL
Elashoff
Robert M
RM
D000328:Adult; D000368:Aged; D001835:Body Weight; D001943:Breast Neoplasms / Q000178:diet therapy* / Q000473:pathology / Q000628:therapy; D018270:Carcinoma, Ductal, Breast / Q000178:diet therapy; D018275:Carcinoma, Lobular / Q000178:diet therapy; D004041:Dietary Fats / Q000008:administration & dosage*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008207:Lymphatic Metastasis; D008875:Middle Aged; D009367:Neoplasm Staging; D016016:Proportional Hazards Models; D016896:Treatment Outcome
D004041:Dietary Fats