Detection and Localization of Unfavorable-histology Prostate Cancer Using MRI and Whole-mount Histopathology

Detecting localized prostate cancer (PC) with metastatic potential-defined as unfavorable-histology PC (uhPC), comprising Grade Group (GG) ≥3 disease or GG 2 disease with cribriform/intraductal features-is critical for guiding appropriate intervention. We evaluated the utility of the Prostate Imaging Reporting and Data System (PI-RADS) and the automated Restriction Spectrum Imaging restriction score (RSIrs; a biophysics-based quantitative MRI biomarker) for uhPC detection and localization.

We evaluated patient-level detection of uhPC in a multicenter cohort with biopsy as the reference standard and lesion-level localization in a separate cohort with whole-mount histopathology (WMHP) from radical prostatectomy. The area under the receiver operating characteristic curve (AUC) was calculated to compare patient-level detection of uhPC using PI-RADS and RSIrs. PI-RADS and RSIrs were used to evaluate sensitivity for the most aggressive tumor within the prostate (index tumor) and for all uhPC tumors on WMHP.

The AUC for patient-level detection of uhPC did not differ significantly between PI-RADS and RSIrs in 1022 patients from five centers (p = 0.13). At the lesion level (n = 103 patients), sensitivity for the index tumor was 87% (95% confidence intervals [CI], 79-94) for PI-RADS, 85% (95% CI, 78-93) for RSIrs, and 93% (95% CI, 86-98) for the two combined. For all uhPC tumors, sensitivity was 81% (95% CI, 73-90) for PI-RADS, 86% (95% CI, 78-93) for RSIrs, and 90% (95% CI, 82-97) for the two combined. A limitation of the lesion-level analyses was that only patients who opted for surgery could be included.

MRI showed high sensitivity for detecting uhPC, reinforcing its value for identifying biologically aggressive disease. Both PI-RADS and automated RSIrs may be useful for targeted biopsy and tumor-focused treatment, such as focal radiation dose escalation to aggressive intraprostatic lesions.