As reported in the Journal of Clinical Oncology by Rowan T. Chlebowski, MD, PhD, and colleagues, 20-year follow-up of the Women’s Health Initiative Dietary Modification trial has shown a maintained reduction in non–breast cancer-related mortality after breast cancer diagnosis and the emergence of a reduction in risk of breast cancer–related mortality in the dietary intervention vs normal diet group.
Rowan T. Chlebowski, MD, PhD
In the trial, 48,835 postmenopausal women aged 50 to 79 years with no history of breast cancer and a dietary fat intake of ≥ 32% of energy were randomly assigned at 40 centers in the United States to a usual diet (60%) or a dietary intervention (40%). The goal in the intervention group was to reduce fat intake to ≤ 20% of energy and increase intake of vegetables, fruits, and grains.
Key Findings
As previously reported, during 8.5 years of dietary intervention, breast cancer incidence and incidence of death as a result of breast cancer were nonsignificantly lower in the dietary intervention group. During this period, death due to breast cancer occurred in 27 (0.016%) vs 61 women (0.024%), with a hazard ratio of 0.67 (95% confidence interval [CI] = 0.43–1.06, P = .08).
After cumulative median follow-up of 19.6 years and occurrence of a total of 3,374 breast cancers, the hazard ratio for breast cancer incidence for the intervention vs control group was 0.95 (95% CI = 0.89–1.02).
As previously reported, there was a significant reduction in death after breast cancer diagnosis in the dietary intervention group both during the intervention period and after a median 16-year follow-up. After 19.6 years of follow-up, a significant reduction has been maintained; death after breast cancer occurred in 359 (0.12%) vs 652 women (0.14%), with a hazard ratio of 0.85 (95% CI = 0.74–0.96, P = .01).
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After 19.6 years of follow-up, a significant reduction in risk of death due to breast cancer has emerged; death due to breast cancer occurred in 132 (0.037%, annualized risk) vs 251 women (0.047%), with a hazard ratio of 0.79 (95% CI = 0.64–0.97, P = .02).
Among 1,764 women diagnosed with breast cancer during the intervention period, postdiagnosis 10-year breast cancer overall survival was 82% in the intervention group vs 78% in the control group (P = .01).
The investigators concluded, “Adoption of a low-fat dietary pattern associated with increased vegetable, fruit, and grain intake, demonstrably achievable by many, may reduce the risk of death as a result of breast cancer in postmenopausal women.”
Dr. Chlebowski, of the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by contracts with the National Heart, Lung, and Blood Institute and additional funding from the National Cancer Institute. For full disclosures of the study authors, visit ascopubs.org.
