Abstract 691: Visualizing differential prostate cancer lesion growth in longitudinal MRIs of patients on active surveillance: Quantitative mapping by Habitat Risk Score and digital pathology.

Abstract Introduction: Active surveillance (AS) is now incorporated into many prostate cancer (PCa) management guidelines to reduce overtreatment, but it requires frequent monitoring because of the risk of disease progression. Improved risk-stratification tools are needed to distinguish indolent from aggressive disease early in surveillance so that the window for curative treatment is not missed. At many institutions, multiparametric MRI (mpMRI) and MRI-ultrasound (MRI-US) fusion biopsies are standard of care for interval monitoring of patients on AS. Here, we show that a quantitative mpMRI system, the Habitat Risk Score (HRS), identifies differential lesion growth on longitudinal mpMRI and correlates strongly with quantitative analysis of digital pathology from radical prostatectomy (RP) specimens. Study Methods: Patients from “MRI-Guided Biopsy Selection of PCa Patients for Active Surveillance versus Treatment: The Miami MAST Trial” (ClinicalTrials.gov: NCT02242773; total accrual = 208) with confirmed PCa underwent 12-36 months of AS prior to RP. The mpMRI exams consisted of T2-weighted (T2W), Dynamic Contrast Enhanced (DCE)-MRI, and Diffusion Weighted Imaging (DWI) acquired according to PI-RADSv2 recommendations. The HRS approach automatically identifies suspicious prostate lesions on mpMRI by assigning a 10-point pixel-by-pixel risk score presented as a heat map, overlaid on the T2W. Longitudinal mpMRI images, biopsy pathology at 12, 24 or 36-months of surveillance and RP specimen pathology were analyzed. The temporal changes in HRS mpMRI volumes were tracked and HRS maps from the last time point (prior to RP) were examined for correlation with H Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 691.