Magnetic Resonance Imaging (MRI)-Adapted Prostate Cancer Risk Tool Incorporating Cribriform and Intraductal Carcinoma

Abstract

Current prostate cancer risk stratification tools are not adapted for magnetic resonance imaging (MRI)-targeted biopsies and do not include the presence of cribriform carcinoma/intraductal carcinoma (CC/IDC), an independent predictor of adverse clinical outcomes. We developed an MRI-adapted prostate cancer risk tool (MAPCaRT), which incorporates CC/IDC presence to the Cancer of the Prostate Risk Assessment (CAPRA) tool. We compared the prognostic power of MAPCaRT with that of CAPRA in MRI-targeted biopsies (n = 266, 2015-2023) and systematic-only biopsies (n = 1291, 2010-2018) that had matched radical prostatectomy. MAPCaRT employs the aggregate core count method for MRI-targeted lesions to calculate percent positive biopsy cores and uses the radiological stage when assessing MRI-targeted biopsies. Point attribution for CC/IDC presence and Gleason score was determined using a Cox proportional hazards model that included the CAPRA score, Gleason score, and CC/IDC status. Based on calculated MAPCaRT and CAPRA scores, patients were classified into the low-risk (0-2), intermediate-risk (3-5), or high-risk (6+) group. Model performance was assessed via the Kaplan-Meier curves, Harrell C-indices, and decision curve analysis for biochemical recurrence-free survival (BCR-FS) and event-free survival (EFS) (metastasis/cancer-specific death). CC/IDC was present in 84 of 266 (32%) MRI-targeted biopsies and 293 of 1291 systematic-only biopsies (23%). The median follow-up time was 3.4 years (IQR, 2.3-5.5 years) for the MRI-targeted biopsy cohort and 5.9 years (IQR, 3.4-8.1 years) for the systematic biopsy cohort. In the MRI-targeted biopsy cohort, MAPCaRT showed substantial improvement of the C-index compared with CAPRA (0.635 vs 0.574, P = .045) and greater net clinical benefit for 4-year BCR-FS. In the systematic biopsy cohort, MAPCaRT demonstrated improved C-index for BCR-FS (0.696 vs 0.655, P < .001) and greater net clinical benefit for 5-year BCR-FS and EFS. Other model performance metrics were marginally better with MAPCaRT. In summary, we developed MAPCaRT (prostatecancercalculator.lmp.utoronto.ca), a modified version of CAPRA incorporating CC/IDC presence, which demonstrated improved BCR-FS and EFS predictions. This may result in better clinical guidance for disease management decisions.

Keywords: biochemical recurrence; event-free survival; magnetic resonance imaging; prostate cancer; prostate cancer outcomes; risk calculator.