Eating more vegetables, fruits, and grains, as part of a low-fat dietary pattern, significantly reduced the risk for death from breast cancer among postmenopausal women, according to results of a study (abstract 520) presented at a presscast ahead of the 2019 American Society of Clinical Oncology (ASCO) Annual Meeting, which will be held May 31–June 4 in Chicago.
“To our review, this is the only study providing randomized clinical trial evidence that an intervention can reduce a woman’s risk of dying from breast cancer,” wrote Rowan T. Chlebowski, MD, PhD, FASCO, of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, in a press release.
Data were from the Women’s Health Initiative (WHI) clinical trial, looking at dietary modification in 48,835 postmenopausal women with no previous history of breast cancer. After long-term follow-up (median, 19.6 years), 3,374 breast cancers were diagnosed. Women who followed a balanced diet that was low in fat and included daily servings of fruits, vegetables, and grains had a 21% lower risk for death from breast cancer compared with women who continued their normal diet (hazard ratio [HR], 0.79; 95% CI, 0.64–0.97).
In addition, there was a 15% reduction in deaths after breast cancer from any cause (HR, 0.85; 95% CI, 0.74–0.96).
“The important thing here is that it is worth us sticking to the message of prevention that what we eat matters,” said Lidia Schapira, MD, FASCO, an ASCO expert on breast cancer. “Postmenopausal women who take the time to think about and plan their diets will be taking an important step toward prevention and improving their health.”
The study included women age 50 to 79 years. From 1993 to 1998, they were randomly assigned to continue their normal diet (60% of patients), in which fat accounted for 32% or more of their daily calories, or a diet with a goal of reducing fat consumption to 20% of energy and which increased vegetable, fruit, and grain intake (40%).
Women assigned to the dietary intervention significantly reduced their fat intake (P < .001), and increased their fruit, vegetable, and grain intake (P < .001), all with a modest weight loss (3%).
“This is a dietary change that we think can be achievable by many because it represents dietary moderation,” Chlebowski said, noting that the diet was even more moderate than originally planned because the majority of patients in the intervention arm did not reach the 20% goal for fat consumption.
An additional analysis scheduled to be presented separately showed that metabolic syndrome score identified a subgroup of postmenopausal women at high risk for death from breast cancer—those with 3 to 4 metabolic abnormalities—who are more likely to benefit from the dietary intervention.
Commenting on the results, ASCO President Monica M. Bertagnolli, MD, FACS, FASCO, pointed out the importance of this being a randomized trial.
“We have been challenged by having only observational trials when it comes to understanding the relationship between diet and deaths from cancer,” Bertagnolli said.
The fact that this study looked at these two populations this far out based on randomized trial data makes it “powerful information,” she added.