Healthy diet may reduce the risk of low-grade prostate cancer progressing to a higher grade

Abstract

Higher adherence to a healthy diet significantly reduced the risk of prostate cancer progression in men with low-risk prostate cancer on active surveillance, according to a study published in JAMA Oncology.¹

The study is the first to show a significant association between a healthy diet and a significantly decreased risk of grade reclassification in this setting, according to the senior author of the study, Bruce J. Trock, PhD, Frank Hinman Jr. Endowed Professor of Urology and professor of oncology and epidemiology at the Johns Hopkins School of Medicine.

Using the Healthy Eating Index (HEI), a validated measure of overall diet quality that adheres to the Dietary Guidelines for Americans developed by the US Department of Agriculture, the study found that the likelihood of disease progression from Grade Group 1 to Grade Group 2 or higher decreased by 30% for every 25-point increase in the HEI. (The HEI provides a score of 0–100 for each category of healthful and unhealthful foods eaten by a person, with higher scores indicating a healthier diet.²)

Even more important, according to Dr Trock, was the finding that a 25-point increase in the HEI significantly decreased (by nearly 50%) the risk of progressing to Grade Group 3 or higher. “This is important because men with Grade 2 can sometimes continue on active surveillance, but the Grade Group 3 nearly always mandates definitive treatment with surgery and/or radiation,” he says.

The prospective cohort study included 886 men diagnosed with Grade Group 1 prostate cancer between January 2005 and February 2017 who were undergoing active surveillance. All the men completed a validated food frequency questionnaire on their usual dietary patterns. Researchers also looked at a measure of how much diet likely contributes to inflammation (i.e., the Dietary Inflammatory Index), but they found no association between this measure and grade reclassification.

Dr Trock says that the findings offer urologists evidence to share with their patients on active surveillance that a healthy diet may improve their prognosis, and they also provide concrete steps that patients can take to play an active role in the management of their disease, something that men on active surveillance often ask about.

“But this isn’t a magic cure-all, and men should continue with their active surveillance regimen,” says Dr Trock, who emphasizes that he would like to see the results of the study replicated in other studies. “But there is no downside to improving your diet quality, and it has other health benefits for cardiovascular disease, diabetes, and weight control,” he adds.

Commenting on the study, Walter M. Stadler, MD, Fred C. Buffett Professor of Medicine and senior advisor to the Comprehensive Cancer Center director at UChicago Medicine, calls the study interesting and agrees that a healthy diet accompanied by regular exercise is always a good idea because of their multiple health benefits.

He cautions, however, that distinguishing the benefits of a healthy diet with respect to disease progression apart from other potential cofactors, such as other health issues (stress, concomitant illnesses, and social determinants of health), is essentially impossible. “It is difficult to determine whether it’s the healthy diet per se or just healthy living,” he says.

He also says that it is impossible to easily distinguish from the study the association of diet with “progression” of prostate cancer from “development” of prostate cancer, because almost all “progression” events on active surveillance are likely due to under-sampling. “In other words, higher grade prostate cancer is already present in a significant proportion of men with Gleason Group 1 disease but was not detected on initial biopsy due to sampling error,” he says, adding that the use of enhanced magnetic resonance imaging–based biopsy algorithms in more recent years is making this issue less prevalent.