A combined MRI-PSAD risk stratification system for prioritizing prostate biopsies.

Introduction:   Prostate cancer screening with PSA is associated with low specificity; furthermore, little is known about the optimal timing of biopsy.  We aimed to evaluate whether a risk classification system combining PSA density (PSAD) and mpMRI can predict clinically significant cancer and determine biopsy timing.
Materials and Methods:  We reviewed the medical records of 256 men with a PI-RADS ≥ 3 lesion on mpMRI who underwent transperineal targeted and systematic biopsies of the prostate between 2017-2019.  Patients were stratified into three risk groups based on PSAD and mpMRI findings. The study endpoint was clinically significant prostate cancer (CSPC).  The association between the risk groups and CSPC was evaluated.
Results:  Based on the proposed risk stratification system 42/256 men (16%) were high-risk (mpMRI finding of extra-prostatic extension and/or seminal vesicle invasion and/or a PI-RADS 5 lesion with a PSAD > 0.15 ng/mL²), 164/256 (64%) intermediate-risk (PI-RADS 4-5 lesions and/or PSAD > 0.15ng/mL² with no high-risk features) and 50/256 (20%) low-risk (PI-RADS 3 lesions and PSAD ≤ 0.15 ng/mL²).  High-risk patients had significantly higher rates of CSPC (76%) when compared to intermediate-risk (26%) and low-risk (4%).  On multivariable logistic regression analysis adjusted for age, previous biopsy, and clinical T-stage we found an association between intermediate-risk (OR = 4.84, p = 0.038) and high-risk (OR = 40.13, p < 0.001) features and CSPC.  High-risk patients had a shorter median biopsy delay time (110 days) compared to intermediate- and low-risk patients (141 and 147 days, respectively).  We did not find an association between biopsy delay and CSPC.
Conclusions:   Our findings suggest that a three-tier risk classification system based on mpMRI and PSAD can identify patients at high-risk for CSPC who may benefit from earlier biopsy.