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

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 and GG ≥ 3 and reclassification to unfavorable intermediate-risk (UIR) disease. Subset analyses were performed for men with (1) MRI before 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 disease, and 5.6% to GG ≥ 3. Of the 306 with positive MRI (Prostate Imaging Reporting and Data System ≥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%, respectively. 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 one-third 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; 95% CI, 2.9%-10% for UIR; 95% CI, 0.8%-5.3% for GG ≥3). Our data support systematic + targeted CBx for men with positive MRI considering AS, whereas men with GG1 cancer and negative MRI should be able to defer CBx.