We aimed to reveal the association between the method of diagnosis (multi-parametric magnetic resonance imaging [mpMRI] and digital rectal examination [DRE]) and oncological outcomes of patients with clinical T3a (cT3a) prostate cancer after radical prostatectomy (RP) and stratify them according to oncological risk. We included 132 cT3a prostate cancer patients who underwent RP between 2008 and 2018. The biochemical recurrence (BCR)-free survival rate was evaluated according to the method of

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... gnosis (mpMRI alone; mpMRI group vs. DRE [with or without mpMRI]; DRE group). Several preoperative factors were evaluated in the multivariate analysis. Patients were divided into risk groups by our prediction model. The mpMRI group had significantly longer BCR-free survival than the DRE group (p<0.0001). The method of diagnosis (hazard ratio [HR]=2.69; 95% confidence interval [CI] 1.45-5.06; p=0.0017) and % positive cores (HR=4.36; 95% CI 1.14-16.5; p=0.031) were independent prognostic factors. Patients were divided into three risk groups based on these factors. There was a significant difference in BCR-free survival rate among the groups (p=0.0002).The method of diagnosis of cT3a prostate cancer was associated with BCR-free survival, and we categorized patients into risk groups. These assessments were attributable to the appropriate therapeutic strategy for patients with cT3a prostate cancer.