A Limited-Versus-Extensive Staging Strategy for Small Cell Prostate Cancer.

Abstract

Small cell prostate cancer (SCPC) is a rare histologic subtype of prostate cancer, for which the optimal staging strategy remains unclear. The Surveillance, Epidemiology, and End Results database was used to analyze the incidence and outcomes of SCPC between the years 2004 through 2016. Limited-stage SCPC (LS-SCPC) was defined as SCPC without any metastasis regardless of local invasion. Extensive stage SCPC (ES-SCPC) was defined as any metastasis to lymph nodes and/or to distant organs. A total of 403 SCPC patients were included in the study cohort, accounting for 0.056% of all prostate cancer cases (n=719,655). Of the 358 patients with known metastasis status, 275 (76.8%) patients had ES-SCPC, whereas 83 (23.2%) patients had LS-SCPC. LS-SCPC was associated with better overall survival (17 vs. 9 mo, P<0.001) and disease-specific survival (25 vs. 10 mo, P<0.001) compared with ES-SCPC. All LS-SCPC patients had a similar overall survival regardless of T stage. Similarly, all ES-SCPC patients had similar outcomes regardless of metastasis sites. High prostate-specific antigen (PSA) is paradoxically associated with superior outcome in both localized stage patients (PSA≥4 vs. PSA<4, 19 vs. 10 mo, P=0.002) and extensive stage patients (PSA≥20 vs. PSA<20, 13 vs. 9 mo, P=0.02). Multivariate analysis of treatment showed that chemotherapy was associated with improved survival in ES-SCPC with hazard ratio of 0.52. Similar to small cell lung cancer, SCPC can be staged into LS-SCPC or ES-SCPC. The binary staging system correlates well with prognosis.