Assessing the oncologic risk when systematic and multiparametric magnetic resonance imaging-targeted prostate biopsy grade groups are discordant

Abstract Background and Objective In the systematic biopsy (SBx) era, prostate biopsy grading followed the rule that the ISUP grade group (GG) assigned was the highest GG of any core. This rule has been retained in the era of multiparametric magnetic resonance imaging (MRI)-guided biopsy in the case of discordance between SBx and targeted (TBx) samples. We assessed whether oncologic risk in patients undergoing SBx and TBx was driven by the highest GG of the two. Methods Overall, 6,588 patients received SBx plus MRI-TBx and radical prostatectomy. We assessed advanced stage (seminal vesicle (SVI) or lymph node invasion (LNI) ± extraprostatic extension (EPE)), adverse pathology (advanced stage or high GG), and biochemical recurrence (BCR) for each SBx and MRI-TBx GG combination. Key Findings and Limitations Overall, 3,405 (52%) had discordant GGs. When SBx and MRI-TBx grades were discordant, the risk of advanced-stage disease was intermediate. For instance, the risk of advanced pathologic stage was 23% for GG3 on both SBx and TBx, and 8.8% for concordant GG2. The risk was 18% for patients with SBx GG3 but TBx GG2, and 15% if the reverse were true. Similar results were seen for other outcomes. Conclusions and Clinical Implications When the GG is discordant between SBx and TBx, the risk is intermediate. The current approach of assigning the highest GG should be abandoned, and urologists should consider de-escalating treatment intensity for patients with discordant SBx and MRI-TBx GGs. Our findings are plausibly explained by pattern 4 volume being the primary driver of risk.