Purpose

To evaluate sub-differentiation of PI-RADS-3 prostate lesions using pre-defined T2- and diffusion-weighted (DWI) MRI criteria, to aid the biopsy decision process.

Methods

143 patients with PIRADS-3 index lesions on MRI underwent targeted transperineal-MR/US fusion biopsy. Radiologists with 2 and 7-years experience performed blinded retrospective second-reads using set criteria and assigned biopsy recommendations. Inter-reader agreement, Gleason score (GS), positive (PPV) predictive values (±95% confidence intervals) were calculated and compared by Fisher’s exact test with Bonferroni-Hom correction.

Results

43% (61/143) patients had GS 6-10 and 21% (30/143) GS ≥ 3 + 4 cancer. For peripheral zone lesions, significant differences in any cancer detection were found for shape (0.26 ± 0.13 geographical vs. 0.69 ± 0.23 rounded; p = 0.0055) and ADC (mild 0.21 ± 0.12 vs marked 0.81 ± 0.19; p = 0.0001). For transition zone, significantly increased cancer detection was shown for location (anterior 0.63 ± 0.15 vs. mid/posterior 0.31 ± 0.14; p = 0.0048), border (pseudo-capsule 0.32 ± 0.14 vs. ill-defined 0.61 ± 0.15; p = 0.0092), and ADC (mild 0.35 ± 0.12 vs marked restriction 0.68 ± 0.17; p = 0.0057). Biopsy recommendations had 62% inter-reader agreement (89/143). Experienced reader PPVs were significantly higher for any cancer with “biopsy-recommended” 0.61 ± 0.11 vs. “no biopsy” 0.21 ± 0.10 (p = 0.0001), and for GS 7-10 cancers: 0.32 ± 0.10 vs. 0.08 ± 0.07, respectively (p = 0.0003).

Conclusion

Identification of certain objective imaging criteria as well as a subjective biopsy recommendation from an experienced radiologist can help to increase the predictive value of equivocal prostate lesions and inform the decision making process of whether or not to biopsy.