Contemporary Comparison of Clinicopathologic Characteristics and Survival Outcomes of Prostate Ductal Carcinoma and Acinar Adenocarcinoma: A Population-Based Study

Prostate cancers of ductal origin (DC) represent a rare entity and were identified in 502 (0.10%) of 469,946 patients with nonmetastatic and 79 (0.39%) of 19,931 patients with metastatic disease in the Surveillance, Epidemiology and End Results database. DC was associated with 1.6- to 2.8-fold higher risk of cancer-specific mortality. Purpose: To investigate clinicopathologic characteristics and cancer-specific mortality (CSM) rates of ductal carci- noma (DC) versus the common acinar adenocarcinoma in nonmetastatic and metastatic (M1) prostate cancer patients. Patients and Methods: Within the Surveillance, Epidemiology, and End Results database (2004-2015), we identified patients with histologically confirmed prostate adenocarcinoma who harbored either DC (n ¼ 581) or acinar adeno- carcinoma (n ¼ 489,296). Kaplan-Meier and 4:1 propensity scoreematched multivariable Cox regression models adjusted for clinical and pathologic parameters were used to test for CSM differences. Three separate analyses were performed on all patients with nonmetastatic disease, patients with nonmetastatic patients treated with radical prostatectomy only, and patients with metastatic disease. Results: DC was identified in 502 (0.10%) of 469,946 patients with nonmetastatic disease and 79 (0.39%) of 19,931 patients with metastatic disease. In patients with nonmetastatic disease, 253 (50.4%) DC patients underwent radical prostatectomy, 61 (12.2%) DC patients received external-beam radiotherapy, and 188 (37.4%) received other treatment modalities. In multivariable analyses, DC was associated with higher CSM in the overall nonmetastatic patient population (hazard ratio [HR] ¼ 1.8; 95% confidence interval [CI], 1.3-2.6; P ¼ .001), in the nonmetastatic radical prostatectomy population (HR ¼ 2.8; 95% CI, 1.3-6.0; P < .01), and in the M1 population (HR ¼ 1.6; 95% CI, 1.1-2.2; P < .01). Conclusion: Prostate cancers of ductal origin represent a rare entity among patients with nonmetastatic disease as well as among patients with metastatic disease, and regardless of stage, DC behaves more aggressively.