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2019 ASCO: Low-Fat Diet May Reduce the Risk of Death From Breast Cancer in Postmenopausal Women

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Key Points

  • The adoption of a diet low in fat and high in vegetables, fruits, and grains significantly reduces the rate of mortality after breast cancer in postmenopausal women.
  • The researchers found that during 8.5 years of dietary intervention, there were 8% fewer breast cancers, and deaths from breast cancer were somewhat fewer in the intervention group, but the rates were not significantly different.

Excluding skin cancer, breast cancer is the most common cancer diagnosed in women in the United States. In 2019, the American Cancer Society estimates that about 268,600 new cases of breast cancer will be diagnosed in women, and about 41,760 women will die from their disease. 

Although observational studies of dietary fat intake and its effect on breast cancer have had inconsistent results, nearly 20-year data from the Women’s Health Initiative Dietary Modification Trial, a randomized clinical trial assessing how a low-fat diet may influence breast cancer incidence and outcome, show that the adoption of a low-fat diet containing increased portions of vegetables, fruits, and grains significantly reduces the risk of death from breast cancer in postmenopausal women. The study by Chlebowski et al will be presented during the 2019 ASCO Annual Meeting (Abstract 520).

Study Methodology and Results

From 1993 to 1998, researchers randomly assigned 48,835 postmenopausal women aged 50 to 79 years with no previous history of breast cancer and a dietary fat intake ≥ 32% of total energy to a usua-diet comparison group (60%) or a dietary-intervention group (40%). The goal was to reduce fat intake to 20% of energy and increase vegetable, fruit, and grain intake.

The dietary-intervention group significantly reduced their fat intake and increased their fruit, vegetable, and grain intake with modest weight loss (3%, all < .001). The researchers found that during 8.5 years of dietary intervention, there were 8% fewer breast cancers, and deaths from breast cancer were somewhat fewer in the intervention group, but the rates were not significantly different. 

However, researchers found that deaths after breast cancer (ie, breast cancer followed by death from any cause) were significantly reduced in the intervention group, both during intervention (hazard ratio [HR] = 0.65, 95% confidence interval [CI] = 0.45–0.95) and through 16.1 years of cumulative follow-up. After a long-term, cumulative follow-up of 19.6 years, with 3,374 incidences of breast cancer, the significant reduction in deaths after breast cancer continued, with 1,011 deaths (HR = 0.85, 95% CI = 0.74–0.96) and a significant reduction in deaths from breast cancer (ie, breast cancer followed by death attributed to the disease) emerged, with 383 deaths (HR = 0.79, 95% CI = 0.64–0.97).

“[The] adoption of a low-fat dietary pattern associated with increased vegetable, fruit, and grain intake, demonstrably achievable by many, significantly reduced the risk of death from breast cancer in postmenopausal women. To our review, these findings provide the first randomized clinical trial evidence that a dietary change can reduce a postmenopausal woman’s risk of dying from breast cancer,” concluded the study authors.

First author Rowan Chlebowski, MD, PhD, also noted that greater uptake of the balanced, low-fat diet could lead to a major reduction in deaths from breast cancer in the United States, as well as savings in health-care costs.

Disclosure: Funding for this study was provided by the National Institutes of Health. For full disclosures of the study authors, visit asco.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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