Diet Quality, Dietary Inflammatory Potential, and Risk of Prostate Cancer Grade Reclassification.

Importance: It remains unclear whether diet may influence the risk of prostate cancer grade reclassification in men undergoing active surveillance.

Objective: To assess the association of diet quality and dietary inflammatory potential with prostate cancer grade reclassification during active surveillance.

Design, Setting, And Participants: This prospective cohort study included men diagnosed with grade group (GG) 1 prostate cancer from January 2005 to February 2017 who were undergoing active surveillance and at active surveillance enrollment prospectively completed a validated food frequency questionnaire regarding their usual dietary patterns. Data were analyzed from October 29, 2023, to June 17, 2024.

Exposures: The Healthy Eating Index 1999-2000 (HEI) and energy-adjusted HEI (E-HEI) scores as a measure of adherence to the Dietary Guidelines for Americans and the Dietary Inflammatory Index (DII) and energy-adjusted DII (E-DII) scores as metrics of dietary inflammatory potential were calculated using self-reported diet data.

Main Outcomes And Measures: A competing risk regression was performed to test the baseline HEI, E-HEI, DII, and E-DII scores for an association with grade reclassification to GG2 or greater or GG3 or greater (ie, extreme grade reclassification) during active surveillance, adjusting for established active surveillance prognostic factors and smoking history at baseline.

Results: The study included 886 men (median age at diagnosis, 66 years [IQR, 61-69 years]). After median follow-up of 6.5 years (IQR, 4.0-9.1 years), 187 (21%) had grade reclassification to GG2 or greater, including 55 (6%) with extreme grade reclassification. The cumulative incidence of grade reclassification was 7% (95% CI, 5%-9%) at 3 years, 15% (95% CI, 12%-17%) at 5 years, and 33% (95% CI, 29%-37%) at 10 years; that of extreme grade reclassification was 2% (95% CI, 1%-4%) at 3 years, 4% (95% CI, 3%-5%) at 5 years, and 10% (95% CI, 7%-13%) at 10 years. Higher baseline HEI (subdistribution hazard ratio [SHR], 0.85; 95% CI, 0.73-0.98; P = .03) and E-HEI (SHR, 0.86; 95% CI, 0.74-1.00; P = .047) per 1-SD increase in score were associated with a significantly lower risk of grade reclassification. Higher baseline HEI (SHR, 0.72; 95% CI, 0.57-0.93; P = .01) and E-HEI (SHR, 0.73; 95% CI, 0.57-0.94; P = .01) per 1-SD increase in score were associated with a significantly lower risk of extreme grade reclassification. Neither the baseline DII nor E-DII was associated with either grade reclassification outcome (eg, for grade reclassification to ≥GG2, the SHR was 1.08 [95% CI, 0.93-1.26] per 1-SD increase in DII score and 1.02 [95% CI, 0.86-1.21] per 1-SD increase in E-DII score).

Conclusions And Relevance: The findings suggest that in men diagnosed with GG1 prostate cancer undergoing active surveillance, higher adherence to American dietary guideline recommendations may be associated with a lower risk of grade reclassification, particularly to GG3 or greater disease, which mandates curative treatment.