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

PurposeTo investigate the impact of multiparametric magnetic resonance imaging (mpMRI) on risk group assessment of patients with prostate cancer (PCa) initially addressed to external beam radiation therapy (EBRT).Materials and methodsWe 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.ResultsPatients 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.ConclusionmpMRI changed clinical risk stratification in about 41% of patients with PCa, with potential impact on EBRT planning.