Cancer-Specific Mortality in Rare Histological Subtypes of Prostate Cancer: Radical Prostatectomy Versus Radiation Therapy

BACKGROUND: Cancer-specific mortality (CSM) rates in patients with rare histological prostate cancer subtypes after treatment with radical prostatectomy (RP) versus radiation therapy (RT) are largely unknown. METHODS: Relying on the Surveillance, Epidemiology, and End Results database (2004-2020), we identified patients with five prostate cancer subtypes treated with RP or RT. Kaplan-Meier analyses and Cox regression models addressed CSM. RESULTS: Of 427,055 patients, 425,692 (99.68%) harbored acinar, 855 (0.20%) ductal, 324 (0.08%) mucinous, 54 (0.01%) signet ring cell adenocarcinoma, and 130 (0.03%) neuroendocrine carcinoma. Of those, 250,910 (59%), 592 (69%), 262 (81%), 34 (63%), and 34 (26%) were treated with RP, respectively. Five-year cancer-specific survival rates after RP versus RT were 99.2 versus 97.1% in acinar; 96.3 versus 87.1% in ductal; 98.7 versus 92.1% in mucinous; 97.0 versus 94.7% in signet ring cell; and 59.4 versus 20.5% in neuroendocrine carcinoma. In univariable Cox regression models, RP was associated with a lower CSM rate in acinar (hazard ratio [HR] 0.28; p < 0.001), ductal (HR 0.25; p < 0.001), and neuroendocrine (HR 0.36; p < 0.001), but not in mucinous (p = 0.052) and signet ring cell carcinoma (p = 0.8). After multivariable adjustment, RP remained an independent predictor of lower CSM in acinar (HR 0.35; p < 0.001), ductal (HR 0.30; p < 0.001), and neuroendocrine carcinoma (HR 0.53; p = 0.042). CONCLUSIONS: Higher CSM was recorded after RT in acinar, ductal, and neuroendocrine carcinoma. Conversely, no differences in CSM were identified when RP was compared with RT in mucinous and signet ring cell adenocarcinoma.