The EAU guidelines recommend to omit confirmatory biopsies in patients on active surveillance (AS) if upfront MRI with systematic (SBx) and targeted (TBx) biopsies are performed (strength rating: weak). This study aims to determine the rate of Grade Group (GG) reclassification at confirmatory biopsies in patients on AS who underwent upfront MRI with TBx.
We selected patients included in the PRIAS study who underwent upfront MRI or MRI within six months after inclusion together with TBx in lesions (≥ PIRADS 3). All patients underwent a second MRI with confirmatory biopsies within two years after inclusion.
Two hundred twelve patients met the inclusion criteria and were analyzed. The median time between the two MRIs was 12 (interquartile range 10-14) months. Sixty-nine percent of the patients (146/212) had a lesion on MRI. Of the 66 patients with no lesion on second MRI, 2(3,0%) and 0(0%) patients reclassified to GG≥2 and ≥3. Of all patients with PIRADS 3, 9(22%) and 3(7.3%) patients reclassified to GG≥2 and ≥3, for PIRADS 4 these numbers are 19(26%) and 8(11%), and for PIRADS 5, 10(32%) and 5(16%) (Table 1). The outcome of both SBx and TBx was known in 111 patients. By not performing SBx 6/32(19%) and 2/14(14%) of the reclassification to GG≥2 and GG≥3 would have been missed, and 9/32(28%) and 5/14(36%) by not performing TBx. Omitting biopsies in patients with a lower PIRADS score on second MRI in comparison to their first MRI would prevent 49/212 (23%) of the biopsies at the cost of missing 18% (7/40) GG≥2 and 18% (3/16) GG ≥3. Limitation of this study is the absence of the PRECISE score.
Based on our results, we conclude that in patients with a negative second MRI confirmatory biopsies can safely be omitted. Both SBx and TBx are indicated if the second MRI shows a lesion (≥ PIRADS 3) because the risk of being reclassified to GG≥2 and GG≥3 exceeds 20% and 5% for all PIRADS scores. In patients with a lower PIRADS score on secondary MRI, biopsies cannot safely be omitted.