Abstract
BACKGROUND: High diet quality may support a metabolic and anti-inflammatory state less conducive to tumour progression. We prospectively investigated diet quality in relation to Gleason grade progression among localised prostate cancer patients on active surveillance, a clinical management strategy of disease monitoring and delayed intervention. METHODS: Men with newly diagnosed Gleason score 6 or 7 prostate cancer enroled on a biennial monitoring regimen. Patients completed a food frequency questionnaire (FFQ) at baseline (n = 411) and first 6-month follow-up (n = 263). Cox proportional hazards models were fitted to evaluate multivariable-adjusted associations of diet quality [defined via the Healthy Eating Index (HEI)-2015] with Gleason grade progression. RESULTS: After a median follow-up of 36 months, 76 men progressed. Following adjustment for clinicopathologic factors, we observed a suggestive inverse association between baseline diet quality and Gleason grade progression [hazard ratio (HR) and 95% confidence interval (CI) for the highest vs. the lowest HEI-2015 tertile: 0.59 (0.32-1.08); P(trend) = 0.06]. We observed no associations with diet quality at 6-month follow-up, nor change in diet quality from baseline. CONCLUSIONS: In localised prostate cancer patients on surveillance, higher diet quality or conformance with United States dietary guidelines at enrolment may lower risk of Gleason grade progression, though additional confirmatory research is needed.