Dietary patterns, nutrients, and prostate cancer grade progression

Background Active surveillance has become established as the preferred initial management strategy for men with favorable-risk prostate cancer, avoiding harms of overtreatment. Emerging evidence suggests that stricter adherence to dietary guideline recommendations may lower risk of disease progression during surveillance. However, it remains unclear which specific dietary patterns and nutrients may be protective. Using prospective data from one of the largest, longest-running active surveillance cohorts, we assessed dietary patterns and nutrients for association with prostate cancer grade progression. Methods We included men diagnosed with grade group (GG) 1 prostate cancer undergoing active surveillance who prospectively completed a validated food frequency questionnaire at baseline. We evaluated each man’s baseline alternate Mediterranean Diet (aMED), Dietary Approaches to Stop Hypertension (DASH) diet, and plant-based diet index (PDI) scores. We performed competing risk proportional hazards regression to test the diet index scores and specific food and nutrient intakes for association with any upgrading (to ≥GG2) and extreme upgrading (to ≥GG3) on a surveillance biopsy, adjusting for baseline clinicopathological prognostic factors and smoking history. Findings: We included 868 men. After median follow-up of 7.9 years (quartiles 4.5–11.6), 207 men experienced upgrading, including 61 with extreme upgrading. A higher baseline PDI score was associated with a lower risk of upgrading (p-trend for quintiles 0.02) and extreme upgrading (0.04). Neither aMED nor DASH score was associated with either upgrading outcome. Alcohol consumption was positively associated with upgrading (subdistribution hazard ratio 1.09, 95% confidence interval 1.002–1.19). Interpretation: In a prospective cohort of nearly 900 men with long-term follow-up, greater adherence to a plant-based dietary pattern was associated with a reduced risk of prostate cancer grade progression on active surveillance, including progression to GG3 or worse disease which mandates curative treatment. These results can inform evidence-based dietary recommendations for men with favorable-risk prostate cancer.