Can a healthy diet prevent cancer progression?

From Dr. Jeannette Schenk, Public Health Sciences Division

For some slow-growing cancers, diagnosed patients lacking additional risk factors might opt to follow active surveillance instead of proceeding to aggressive, curative treatments with adverse side effects. This practice is common in prostate cancer, where “men diagnosed with lower risk prostate cancer are increasingly managed via active surveillance,” explained Dr. Jeannette Schenk, senior staff scientist in the Fred Hutch Cancer Prevention Program and part of the Division of Public Health Sciences. In this approach, patients “undergo periodic prostate-specific antigen (PSA) blood tests, digital rectal exams and surveillance biopsies with definitive treatment recommended for disease progression. Despite their initial low-risk status, up to 50% of men with prostate cancer on active surveillance experience adverse grade reclassification and curative intent treatment is recommended. The heterogenous disease course of low-risk prostate cancers underscores the importance of secondary prevention, and there is growing interest in determining whether modifiable lifestyle factors, such as diet, may prevent or delay progression,” Schenk adds. This question of whether a healthy diet might prevent prostate cancer progression was investigated in a recent Nutrition and Cancer study led by Dr. Schenk and a research group comprised of University of Washington and Fred Hutch researchers, including Dr. Daniel Lin, principal investigator of the Canary Prostate Active Surveillance Study.

Schenk explains that, “the Canary Prostate Active Surveillance Study (PASS) is a multicenter prospective cohort of men diagnosed with clinically localized prostate cancer whose treatment plan was active surveillance to manage their prostate cancer.” This study began in 2008 and “has enrolled more than 2,000 men from 10 clinical sites throughout North America.” To understand the role of a healthy diet in prevention of prostate cancer progression, Schenk et al. analyzed data from 564 men enrolled in PASS over nearly 8 years. In addition to their clinical exams to monitor disease progression, the height and body weight of each man was recorded and used to calculate body mass index (BMI). Participants were also given a self-administered Food Frequency Questionnaire which was developed by the Fred Hutch Nutrition Assessment Shared Resource, to determine diet quality. This survey asked about how much and how often participants consumed items on a list of 120 foods and beverages over the previous 3 months. These food responses were then converted to estimate daily nutrition intake, and diet quality was measured using several dietary indices. These included the Healthy Eating Index (HEI)-2015 which emphasizes food beneficial for overall health like fruits, vegetables and lean proteins and the alternative Mediterranean Diet (aMED) which reflects a diet rich in monosaturated fats, like olive oil, in addition to plant proteins and fish, but low in red meat and refined grains. In addition, they also assessed Dietary Approaches to Stop Hypertension (DASH) which focuses on eating foods and nutrients that are beneficial (fruits, vegetables, whole grains, low-fat dairy) and minimizing others (red meat, refined grains, sodium). The researchers then calculated index scores for each patient with higher scores representing high-quality diets. Using statistical analyses, the authors then asked whether eating a healthy diet was associated with grade reclassification, a surrogate measure of disease progression.

fruit, vegetables and pills going into a jar.
Food is medicine AI-generated image using DALL-E.

Over the 7.8-year course of active surveillance, 42% of men experienced grade reclassification. After adjusting for risk factors that could impact disease progression or other factors that could bias their results, Schenk et al. found a slight correlation between high-quality diets and lower risk of grade reclassification, however these associations were not statistically significant. “One particular challenge inherent in all studies relying on self-reported dietary intake is the presence of non-differential measurement error, which in combination with the relatively small study sample for our analyses, may have limited our ability to detect associations between diet quality and grade reclassification,” Schenk notes.

Even though this study did not find a statistically significant correlation between eating a healthy diet and slower disease progression, we shouldn’t be so quick to dismiss the benefits of reaching for an apple over a Snickers. Dr. Schenk explains, “Although our results do not suggest that higher adherence to the HEI-2015, aMED or DASH diet patterns provide benefit in terms of Gleason Grade reclassification, these dietary patterns have well-established protective effects on many chronic diseases and mortality and remain a prudent choice for men with prostate cancer managed by active surveillance.” She concludes by explaining that future work will “evaluate the relationships between other modifiable lifestyle factors, such as alcohol use, obesity and physical activity and risk of reclassification during active surveillance.”

This work was supported by the National Cancer Institute.

Fred Hutch/University of Washington/Seattle Children's Cancer Consortium members Marian Neuhouser, Yingye Zheng, William Ellis and Daniel Lin contributed to this work.

Schenk JM, Liu M, Neuhouser ML, Newcomb LF, Zheng Y, Zhu K, Brooks JD, Carroll PR, Dash A, Ellis WJ, Filson CP, Gleave ME, Liss M, Martin FM, Morgan TM, Wagner AA, Lin DW. Dietary Patterns and Risk of Gleason Grade Progression among Men on Active Surveillance for Prostate Cancer: Results from the Canary Prostate Active Surveillance Study. Nutr Cancer. 2022 Nov 7:1-9. doi: 10.1080/01635581.2022.2143537. Epub ahead of print. PMID: 36343223.