Routine prostate biopsy reports carry grade-specific tumor burden information beyond the highest Grade Group.

Abstract

Routine prostate biopsy reports contain quantitative information that is lost when a case is reduced to the single highest Grade Group (GG). We examined whether GG-specific tumor burden in routine biopsy reports provides information on radical prostatectomy (RP) pathology beyond the highest biopsy GG. This retrospective single-institution study included 508 analyzable paired biopsy-RP cases from 2014 to 2026. For GG3, GG4, and GG5, burden was reconstructed as the number of positive reporting units and summed cancer length. Firth penalized logistic regression adjusted for highest biopsy GG and non-target GG3-GG5 burden. The focused endpoints were RP GG4-5 for GG4 burden, pT3 or higher disease for GG3 burden, and RP GG5 for GG5 burden. For count models, odds ratios (ORs) were expressed per additional target reporting unit. GG4 count was associated with RP GG4-5 (OR, 1.72; 95% confidence interval [CI], 1.29-2.29), GG3 count with pT3 or higher disease (OR, 1.72; 95% CI, 1.41-2.10; n=473), and GG5 count with RP GG5 (OR, 3.46; 95% CI, 1.40-8.59). Corresponding cancer-length measures showed concordant associations, and the strict 318-case quality-control sensitivity subset yielded similar estimates. Adding target GG burden to models already containing highest biopsy GG and non-target GG burden yielded optimism-corrected area-under-the-curve gains of 0.029 for GG4 count, 0.042 for GG3 count, and 0.010 for GG5 count. Grade-specific burden already present in routine biopsy reports therefore provides complementary information on subsequent RP grade and local stage beyond the highest biopsy GG alone.