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Low-Fat Dietary Pattern and Breast Cancer Mortality in the Women's Health Initiative Randomized Controlled Trial.
Chlebowski, RT, Aragaki, AK, Anderson, GL, Thomson, CA, Manson, JE, Simon, MS, Howard, BV, Rohan, TE, Snetselar, L, Lane, D, et al
Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2017;35(25):2919-2926
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In the Women’s Health Initiative Dietary Modification (WHI DM) trial, 48,835 postmenopausal women were randomly assigned to a dietary modification group or usual diet comparison group to assess low-fat dietary pattern effects on breast cancer incidence. The aim of this study was to present results of dietary modification influence on deaths as a result of breast cancer and on the more general outcome of deaths after breast cancer (breast cancer followed by death as a result of any cause). The study recruited postmenopausal women between 50 and 79 years of age with no record of previous breast cancer. The participants were randomly assigned to a low-fat dietary pattern intervention group or a usual diet comparison group. Results indicate that with long-term follow-up of the WHI DM trial, deaths after breast cancer were significantly reduced in the low-fat dietary group both during the dietary intervention period and throughout the 16.1-year cumulative follow-up period. Authors conclude that women assigned to a low-fat dietary pattern had a significantly reduced risk of death from breast cancer.
Abstract
Purpose Earlier Women's Health Initiative Dietary Modification trial findings suggested that a low-fat eating pattern may reduce breast cancers with greater mortality. Therefore, as a primary outcome-related analysis from a randomized prevention trial, we examined the long-term influence of this intervention on deaths as a result of and after breast cancer during 8.5 years (median) of dietary intervention and cumulatively for all breast cancers diagnosed during 16.1 years (median) of follow-up. Patients and Methods The trial randomly assigned 48,835 postmenopausal women with normal mammograms and without prior breast cancer from 1993 to 1998 at 40 US clinical centers to a dietary intervention with goals of a reduction of fat intake to 20% of energy and an increased intake of fruits, vegetables, and grains (40%; n = 19,541) or to a usual diet comparison (60%; n = 29,294). Results In the dietary group, fat intake and body weight decreased (all P < .001). During the 8.5-year dietary intervention, with 1,764 incident breast cancers, fewer deaths occurred as a result of breast cancer in the dietary group, which was not statistically significant (27 deaths [0.016% per year] v 61 deaths [0.024% per year]; hazard ratio [HR], 0.67; 95% CI, 0.43 to 1.06; P = .08). During the same period, deaths after breast cancer (n = 134) were significantly reduced (40 deaths [0.025% per year] v 94 deaths [0.038% per year]; HR, 0.65; 95% CI, 0.45 to 0.94; P = .02) by the dietary intervention. During the 16.1-year follow-up, with 3,030 incident breast cancers, deaths after breast cancer also were significantly reduced (234 deaths [0.085% per year] v 443 deaths [0.11% per year]; HR, 0.82; 95% CI, 0.70 to 0.96; P = .01) in the dietary group. Conclusion Compared with a usual diet comparison group, a low-fat dietary pattern led to a lower incidence of deaths after breast cancer.