Abstract
INTRODUCTION: Accurate staging of prostate cancer is essential for treatment planning and prognosis. While digital rectal exam (DRE) has traditionally been used, its limitations in detecting extracapsular extension (ECE) have led to increased reliance on multiparametric magnetic resonance imaging (mpMRI). METHODS: This study compared outcomes between T3 prostate cancer diagnosed by DRE vs. mpMRI only (i.e., not T3 by DRE) using data from the Alberta Prostate Cancer Research Initiative. The cohort included all 536 patients with cT3NxMx prostate cancer diagnosed between July 2014 and July 2024. The primary outcome was overall survival, with secondary outcomes including age at diagnosis, prostate-specific antigen (PSA) at diagnosis, treatment modality, Gleason grade group, and metastasis at diagnosis. RESULTS: Patients diagnosed as T3 by DRE were significantly older (71.6 vs. 67.9, p<0.001), had higher PSA levels (32% vs. 11% PSA >20 ng/ml, p<0.001), and higher Gleason grade groups (39% vs. 15% GG4+, p<0.001) compared to those diagnosed by mpMRI. DRE-diagnosed patients underwent radiation therapy and primary androgen deprivation therapy more frequently than MRI-diagnosed patients. DRE-diagnosed patients also had higher rates of metastases at diagnosis (16% vs. 5%, p<0.001) and worse overall survival (hazard ratio 4.6, 95% confidence interval 1.4-15.0, p=0.002). CONCLUSIONS: T3 prostate cancer diagnosed by DRE is associated with more advanced disease, higher metastasis rates, and worse survival compared to mpMRI-diagnosed T3 disease. These findings suggest that T3 disease identified by DRE represents a more aggressive cancer subtype and should be considered higher-risk in clinical decision-making.