MRI prostate tumor volume predicts the need for systematic biopsies in patients undergoing MRI-targeted biopsy.

[BACKGROUND] Combined transrectal mpMRI-TRUS targeted (TB) and systematic biopsy (SB) is widely used to diagnose prostate cancer (PCa). However, SB may be omitted in a subset of patients with minimal risk of missing clinically significant prostate cancer (csPCa) in TB alone. We aimed to identify clinical characteristics predicting the need for SB in men undergoing TB.

[METHODS] In this retrospective cohort study, 879 patients underwent combined TB and SB. Cases where csPCa was missed by TB but detected by SB were identified. Logistic regression analysis was used to identify clinical predictors for SB necessity, including digital rectal examination, prior negative biopsy, age, prostate-specific antigen (PSA), prostate volume, PSA density, mpMRI tumor volume (MTV), number of mpMRI lesions, PI-RADS score, and mpMRI tesla.

[RESULTS] In 80 (9.1%) cases csPCa was missed by TB and detected by SB only. Median MTV was 0.75 cm (IQR 0.43-1.41 cm). Multivariable logistic regression analysis revealed MTV as the only significant predictor of csPCa missed by TB alone (OR=0.52, 95% CI 0.36, 0.75, P<0.001). A larger MTV was inversely associated with the risk of missing csPCa in TB alone. In patients with an MTV greater than 1.36 cm, the rate of missing csPCa with TB alone was ≤5%.

[CONCLUSIONS] MTV is a promising predictor to identify patients who may not require a concomitant SB when undergoing TB. However, this finding needs to be validated in external cohorts before being applied in clinical practice.