Impact of Discordance Between Magnetic Resonance Imaging and Ultrasound Volume Measurements on Prostate Fusion Biopsy Outcomes

To determine whether the difference between MRI-based and ultrasound (US)-based volume measurements are associated with MRI/US-targeted fusion-guided biopsy outcomes. This retrospective, single-center study involved 4177 consecutive patients biopsied between 2010 and 2023 using both MRI/US-targeted fusion and systematic biopsy. Biopsies were indicated because of elevated PSA levels or abnormal multiparametric MRI results. US volume measurements were calculated using the triplane ellipsoid formula, and MRI volumes were obtained by semiautomatic planimetric segmentation. Performance of fusion biopsy compared with systematic biopsy was analyzed with respect to the discordance between MRI and US volume measurements. In 2736 patients (66%), biopsy detected prostate cancer. In cases where both techniques yielded prostate cancers (1695/2736 [62%]), a statistically higher proportion of patients had higher Gleason scores on MRI/US-targeted fusion biopsy compared with systematic biopsy (343 patients [20.2%] vs 137 patients [8.1%], P < .001). MRI volume measurements were significantly smaller compared with US volume measurements (median [IQR] 54 mL [39-77], 56 mL [40-80], respectively, P < .001). Beyond 5 mL volume discordance, MRI/US-targeted fusion biopsy gradually showed less added diagnostic benefit compared with systematic biopsy. In the ≤ 5 mL cohort, MRI/US-targeted fusion biopsy detected more aggressive tumors in 4 times as many patients than systematic biopsy (136 vs 32 patients, P < .001). Although MRI/US-targeted fusion biopsy detected more prostate cancers than systematic biopsy, the performance of MRI/US-targeted fusion biopsy declined with more discordance between volumes measured in MRI vs US. Awareness of volume discordance in MRI and US-based volume measurements should alert the operator about the possibility of reduced performance of MRI/US-targeted fusion biopsy.