Detection and Localization of Unfavorable-histology Prostate Cancer Using MRI and Whole-mount Histopathology.
BACKGROUND AND OBJECTIVE 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. METHODS 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. KEY FINDINGS AND LIMITATIONS 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. CONCLUSIONS AND CLINICAL IMPLICATIONS 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.