Plant-based dietary indices and quality of life in men with prostate cancer.

Abstract

356 Background: Prostate cancer is the most prevalent malignancy among US males, with >3.1 million survivors nationally. Treatment-related side effects in the sexual, urinary, bowel, physical, and mental health domains substantially impact quality of life (QOL). Plant-based diets may be associated with better QOL through improved vascular health and anti-inflammatory properties. Methods: This longitudinal cohort study included 1,531 participants with clinically localized (stage T1-T3) prostate cancer managed with primary treatment or active surveillance from the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) Diet and Lifestyle sub-study. Participants completed post-diagnosis food frequency questionnaires (FFQ) in 2004-2006. Plant-based diet index (PDI, emphasizing all plant foods regardless of nutritional quality) and healthful plant-based diet index (hPDI, emphasizing nutritionally beneficial plant foods) were calculated based on 18 food groups, with higher scores indicating higher adherence. Serial QOL assessments (median 14 per participant), including the UCLA Prostate Cancer Index for sexual, urinary, and bowel domains, and SF-36 for physical function and mental health, were obtained prospectively over 14.7 years, with a median follow-up of 3.7 years per participant. Participants were censored at the time of additional treatment. Multivariable linear mixed models examined relationships between dietary indices (quintiles) and QOL scores. Primary models adjusted for time from diagnosis to FFQ, time from FFQ to QOL survey, age at diagnosis, CAPRA (Cancer of the Prostate Risk Assessment) score, treatment group, calories, body mass index, smoking status, alcohol, and physical activity. Results: Participants were diagnosed at a median age of 65 years. Higher PDI scores were associated with better sexual function, bowel function, physical function, and mental health, and less sexual bother and bowel bother (all linear p-trend<0.05), with no association for urinary function or bother. The largest relative difference between extreme quintiles of PDI was for sexual function (11% Q5 vs. Q1; 31.6 ± 1.1 vs. 28.4 ± 1.0). Higher hPDI scores were also associated with better bowel function, physical function, and mental health, and less sexual bother and bowel bother (all p-trend<0.05), with a suggestive positive trend for sexual function (p-trend=0.054) and no associations for urinary domains. The largest relative difference between extreme quintiles of hPDI was for physical function (7.4%, Q5 vs Q1: 82.64±0.69 vs. 76.96±0.76). Conclusions: In prostate cancer survivors, eating more plant-based foods after diagnosis was associated with better QOL across multiple domains, especially sexual function. These results are encouraging given the increasing number of survivors living for many years with prostate cancer who often ask if there is anything they can do to improve their QOL.