Additive Diagnostic Value of Biparametric 3T MRI for Prostate Cancer Detection in PSA Gray-Zone Patients

Introduction: Prostate-specific antigen (PSA) levels between 4.0 and 9.9 ng/mL (the “gray zone”) present a diagnostic challenge, often leading to unnecessary prostate biopsies. We evaluated the additive diagnostic value of biparametric 3T MRI—particularly diffusion-weighted imaging (DWI) with a b-value of 2000—for detecting prostate cancer in these patients.

Methods: Consecutive patients with gray-zone PSA levels (n=446) were prospectively enrolled between July 2014 and August 2022. Transrectal ultrasound-guided prostate biopsy was performed in patients with positive MRI findings or in those whose PSA levels rose on three consecutive tests or exceeded 10 ng/mL during follow-up. All patients were monitored for at least 2 years. Two predictive models—incorporating MRI findings or not—were compared using receiver operating characteristic (ROC) analysis, category-free net reclassification improvement, and integrated discrimination improvement (IDI).

Results: The addition of MRI findings improved the ROC area from 0.764 to 0.933 (p < 0.001), and helped reclassify 84.5% of non-events (95% CI: 78.2–90.7) to a lower-risk category and 72.8% of events (95% CI: 61.7–83.9) to a higher-risk category. The IDI increased by 0.453 (95% CI: 0.402–0.505).

Conclusions: Biparametric MRI offers diagnostic value in patients with PSA levels in the gray zone, beyond conventional clinical predictors.

Keywords: PSA. Prostate Cancer, MRI, b-value, Diagnosis.