Impact of multiparametric magnetic resonance imaging on risk group assessment of patients with prostate cancer addressed to external beam radiation therapy

Purpose: To investigate the impact of multiparametric MRI (mpMRI) on risk group assessment of patients with prostate cancer (PCa) initially addressed to External Beam Radiation Therapy (EBRT). Materials and Methods: we prospectively performed mpMRI (3.0Tsystem) in 44 patients addressed to EBRT, using a multiparametric protocol (high-resolution multiplanar T2-weighted, Diffusion-weighted and dynamic contrast-enhanced imaging). Risk group was assessed in accordance with the National Comprehensive Cancer Network (NCCN) categories, by combining prostate-specific-antigen level, Gleason score and the T-stage as established by digital rectal examination (clinical risk assessment; c-RA) versus mpMRI (mpMRI-risk assessment; mpMRI-RA). The agreement between c-RA and mpMRI-RA was investigated using Cohen’s kappa. Results: Patients were included in very low/low risk, intermediate risk, high risk, very high risk and metastatic NCCN categories in 10 (22.7%), 18 (40.9%), 15 (34.1%), 1 (2.3%) and 0 cases using c-RA vs. 8 (18.2%), 14 (31.8%), 14 (31.8%), 4 (9.1%) and 4 (9.1%) cases using mpMRI-RA, respectively, with only moderate agreement (k = 0.43). MpMRI-RA determined risk downgrading in 2/44 patients (4.5%), and risk upgrading in 16/44 patients (36.3%). After mpMRI, EBRT remained indicated in all patients. Conclusion: mpMRI changed clinical risk stratification in about 41% of patients with PCa, with potential impact on EBRT planning.