Is Confirmatory Biopsy Still Necessary for Active Surveillance of Men With Grade Group 1 Prostate Cancer in the Era of Multiparametric Magnetic Resonance Imaging?

Purpose: Men diagnosed with prostate cancer (PCa) considering active surveillance (AS) are recommended confirmatory biopsy (CBx). Whether this is necessary in the era of MRI-informed biopsies is questionable. Materials and Methods: We studied men with Grade Group [GG] 1 PCa at diagnostic biopsy (DBx) considering AS who underwent MRI and CBx (systematic + targeted) within 18 months. Outcomes were grade reclassification to GG ≥ 2, GG ≥ 3, and reclassification to unfavorable intermediate risk disease (UIR). Subset analyses were performed for men with (1) MRI prior to DBx and (2) MRI after DBx. Results: Five hundred twenty-two men had GG1 PCa at DBx. At CBx, 20% reclassified to GG ≥ 2, 12% to UIR, and 5.6% to GG ≥ 3. Of the 306 with positive MRI (PI-RADS > 3), 27% reclassified to GG ≥ 2 and 16% to UIR disease; men with negative MRI experienced these outcomes at rates of 9.2% and 5.5%. There were no differences in reclassification outcomes based on MRI timing (group A vs B), and neither PSA density nor prostate volume added to MRI information. In men with MRI targets, approximately 1/3 of GG > 2 reclassification events were only captured by systematic biopsy core(s). Conclusions: Reclassification rates at CBx were high in men with positive MRI, but < 10% for all reclassification outcomes in men with negative MRI (95% CI 5.8%-14% for GG > 2, 2.9%-10% for UIR, 0.8%-5.3% for GG > 3). Our data support systematic + targeted CBx for men with positive MRI considering AS, while men with GG1 cancer and negative MRI should be able to defer CBx.