Comparison of the incidence of clinically significant prostate cancer in patients with isolated peripheral versus transitional zone PIRADS 3 lesions.

Introduction: We sought to investigate the association between isolated PIRADS 3 lesions of the transitional zone (TZ) versus the peripheral zone (PZ) and the incidence of clinically significant prostate cancer (csPCa) on systematic and targeted prostate biopsy (SB, TB).

Methods: We retrospectively reviewed our tertiary institutional database of patients who underwent mpMRI-fusion followed by TB + SB between 2016 and 2021. We compared the incidence of csPCa (Gleason Grade Group ⩾ 2) in patients with solitary TZ-only PIRADS 3 and PZ-only PIRADS 3 on SB and TB. We excluded patients with (1)known PCa, (2)PIRADS 4-5 and/or (3)lesions in both TZ and PZ. T-tests, Chi-square tests, were conducted to compare between the groups.

Results: Of 1913 patients, we identified 110 with PZ-only and 38 with TZ-only PIRADS 3 lesions. 73 patients in PZ-only and 19 in TZ-only met inclusion criteria. No statistically significant differences were observed between PZ and TZ groups in terms of age, median prostate-specific antigen (PSA), prostate volume, median PSA-density, or median number of targeted cores obtained, all with p > 0.05.On SB, the incidence of csPCA was higher in patients with PZ rather than TZ PIRADS-3 lesions (10/73 vs 1/19, p = 0.28). Similarly, csPCA was more common in TB of PZ versus TZ PIRADS 3 lesions (7/73 vs 0/19, p = 0.33). Based on these results, the positive predictive values of PIRADS3 as a marker of csPCA were 5.3% and 0% for TZ lesions on SB versus TB, respectively, compared to 17.7% and 9.6% in the PZ.

Conclusions: PIRADS 3 lesions are rarely associated with csPCA on SB and TB, particularly when located in the TZ, which is an important factor to consider when deciding on a biopsy in patients with isolated TZ lesions.