Low-Fat Dietary Pattern and Breast Cancer Mortality in the Women’s Health Initiative Randomized Controlled Trial

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 MethodsThe 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). ResultsIn the dietary group, fat intake and body weight decreased (all P , .001). During the 8. ConclusionCompared with a usual diet comparison group, a low-fat dietary pattern led to a lower incidence of deaths after breast cancer.

Association of Low-Fat Dietary Pattern With Breast Cancer Overall Survival

“…Women continued dietary group activities after breast cancer diagnosis, 3 and the cumulative distribution of the duration of dietary intervention before and after breast cancer diagnosis is shown in eFigure 2 in the Supplement. Women with breast cancer participated in the dietary intervention for a median of 4.5 (interquartile range, 2.4-6.3) years before breast cancer diagnosis and a median of 4.0 (interquartile range, 2.3-6.0) years after diagnosis (eFigure 2 in the Supplement).…”

“…The focus on breast cancer cases diagnosed during the dietary intervention period was based on earlier temporal trend study findings, 3,8 which suggested that it was unlikely that outcome of breast cancers diagnosed postintervention, when there was no contact with the dietary modification program, would differ between randomization groups. In the present analyses, a temporal trend for greater improvement in breast cancer overall survival is seen as dietary intervention duration increases.…”

“…In addition, physical activity did not significantly differ between groups. 3 In the present report, we examined, as the primary analyses, dietary modification influence on breast cancer overall survival (breast cancer followed by death from any cause) for the 1764 breast cancer cases diagnosed during the dietary intervention period and followed through September 2013. Note that breast cancer overall survival, defined in the same way, is a commonly accepted end point in adjuvant breast cancer trials.…”

“…3 Subsequent median cumulative follow-up through 16.1 years found deaths after breast cancer, measured from randomization, to be significantly reduced in the dietary intervention group (HR, 0.82; 95% CI, 0.70-0.96; P = .01). 3 These findings suggested that following a low-fat dietary pattern may reduce breast cancers associated with greater mortality. However, as prior analyses of mortality were measured from randomization, it is unclear to what extent the results were driven by dietary influence on postdiagnosis survival.…”

Obesity, Dietary Factors, Nutrition, and Breast Cancer Risk

“…Dietary patterns are likely to vary between populations, because of geographic characteristics and cultural differences in food habits, preferences, and availability [125]. Several studies investigating dietary patterns and breast cancer risk have documented an inverse association with a prudent/low fat dietary pattern, which includes the high intake of vegetables, fruits, whole grains, and fish [110, 111, 124, 126], and a positive association with the less healthy Western diet, which is generally characterized by large quantities of red meat, refined grains, potatoes, and fat [127]. …”