Following a cohort of postmenopausal women for almost 20 years has turned up what is being reported as “proof” that a dietary intervention can prevent breast cancer deaths.

That was the take home message offered by Rowan T. Chlebowski, MD, PhD, of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, California, during a press briefing highlighting a sampling of studies accepted for the American Society of Clinical Oncology meeting.

Chlebowski hangs that claim on analysis of long-term follow-up of women enrolled in the Women’s Health Initiative (WHI), a National Institutes of Health study of 48,835 postmenopausal women. The WHI had a lot of moving parts, one of which randomized women to a low-fat dietary intervention while half the sample followed a normal diet. After more than 8 years, the women in the low-fat arm lost about 3% of body weight, but did not have a statistically significant lower risk of invasive breast cancer. But at that time the researchers added a hopeful note that they observed nonsignificant trends “suggesting reduced risk associated with a low-fat dietary pattern indicate that longer, planned, nonintervention follow-up may yield a more definitive comparison.”

Chlebowski and colleagues now detail the results from that “longer, planned, nonintervention follow-up,” and report: “Now, after long-term, cumulative 19.6 year (median) follow-up, with 3,374 incident breast cancers, 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 (breast cancer followed by death attributed to the breast cancer) emerged (with 383 deaths, HR 0.79 95% CI 0.64- 0.97).” That’s a 15% reduction in all-cause mortality after a breast cancer diagnosis and a 21% lower risk of breast cancer mortality among women following what Chlebowski called a very “doable, balanced diet that cut fat intake to about 20-25% of calories and increased fruits, grains and vegetables.”

ASCO president Monica M. Bertagnolli put it this way: “There is no downside to this.”

ASCO Abstract 520: “Low-fat dietary pattern and long-term breast cancer incidence and mortality: The Women’s Health Initiative randomized clinical trial.”

The ASCO meeting, which kicks off May 31 in Chicago, will feature 2,400 abstracts, and another 3,200 submitted abstracts will be published online. Follow BreakingMED coverage at Physicians’ Weekly.

Read the full ASCO 2019 RoundUp


Peggy Peck, Editor-in-Chief at BreakingMED, a service of @Point of Care, LLC, which provides daily medical news reports curated to serve the unique needs of busy physicians and other healthcare professionals.