Small cell carcinoma of the prostate: National patterns of care and outcomes.

Abstract

9 Background: Small cell prostate cancer (SCPC) is a rare entity with treatment patterns extrapolated from small cell cancer of the lung. Outcomes have been evaluated in small series but prognostic factors are relatively poorly defined. Methods: We utilized the National Cancer Data Base to analyze men diagnosed with SCPC from 2004-2015. Only men with known clinical TNM staging, treatment modalities, and follow up were included. Overall survival (OS) was analyzed and compared with Kaplan-Meier, log-rank, and Cox proportional hazards ratios. Associations with baseline and tumor properties were performed with Chi-squared, independent t-test, and bivariate regression analyses. Results: 800 men with SCPC were identified. Median PSA was 79.0 ng/dL. 55.6% of men had cM1 disease at diagnosis, 31.4% had cN0M0 disease, and 13.0% were cN1M0. Median follow up was 12.4 months for all patients and 19.3 months for cM0 patients. Median survival for cM1, cN0M0, and cN1M0 patients was 9.8, 28.5, and 17.1 months, respectively (p<0.001). In cM0 patients, 66 (18.7%) underwent radical prostatectomy (RP), 177 (50.1%) received radiation therapy (XRT), and 195 (45.2%) received chemotherapy (CT). Median survival for men undergoing RP was not reached vs those who did not undergo RP (p<0.001). XRT also showed a trend towards improved median OS (25.2 vs. 19.1 months, p=0.139). On multivariable analysis for cM0 men, only age (HR 1.044 [95% CI 1.025-10.64] p<0.001), cN1 (HR 1.378 [95% CI 1.001-1.898] p=0.050, RP (HR 0.429 [95% CI 0.259-0.709] p=0.001), and XRT (HR 0.520 [95% CI 0.384-0.704] p<0.001) were predictive for overall survival. When examining only men who received systemic therapy, XRT was the only additional treatment modality to exhibit a survival benefit (HR 0.623 [95% CI 0.425-0.912] p=0.015). Of men with cM1 disease, 78 (17.5%) underwent definitive local therapy (RP/XRT), but no difference in OS was observed. Conclusions: Small cell prostate cancer is an aggressive disease with the majority of men presenting with metastases. In those with pelvis-confined disease who are fit for systemic therapy, radiation therapy to the primary should be considered.