Geographic Differences in Baseline Prostate Inflammation and Relationship with Subsequent Prostate Cancer Risk: Results from the Multinational REDUCE Trial

Background: Prostate cancer incidence rates vary 25-fold worldwide. Differences in PSA screening are largely, but not entirely, responsible. We examined geographic differences in prevalence of histologic prostate inflammation and subsequent prostate cancer risk.

Methods: Seven thousand nonHispanic white men were enrolled in the REduction by DUtasteride of prostate Cancer Events (REDUCE) trial from Europe (n = 4,644), North America (n = 1,746), South America (n = 466), and Australia/New Zealand (n = 144). Histologic inflammation in baseline negative prostate biopsies was classified as chronic (lymphocytes/macrophages) or acute (neutrophils). Multivariable logistic regression was used to examine associations between region and prostate inflammation, and between region and prostate cancer risk at 2-year biopsy.

Results: Prevalence of prostate inflammation varied across region, with broadly similar patterns for acute and chronic inflammation. Relative to Europe, prevalence of acute inflammation was higher in North America [odds ratio (OR), 1.77; 95% confidence interval (CI), 1.51–2.08] and Australia/New Zealand (OR, 2.07; 95% CI, 1.40–3.06). Men from these regions had lower prostate cancer risk than Europeans at biopsy. Among North Americans, prevalence of acute inflammation was higher in Canada versus the United States (OR, 1.40; 95% CI, 1.07–1.83), but prostate cancer risk did not differ between these regions. Among Europeans, prevalence of acute inflammation was lower in Northern and Eastern (OR, 0.79; 95% CI, 0.65–0.97 and OR 0.62; 95% CI, 0.45–0.87, respectively), relative to Western Europe, and these men had higher prostate cancer risk at biopsy.

Conclusions: Prevalence of histologic prostate inflammation varied by region. Geographic differences in prostate inflammation tracked inversely with geographic differences in prostate cancer risk.

Impact: Characterization of premalignant prostate biology and the relationship with subsequent prostate cancer risk could inform prostate cancer prevention efforts. Cancer Epidemiol Biomarkers Prev; 27(7); 783–9. ©2018 AACR.

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