Abstract 4189: Limited-versus-extensive staging system for small cell prostate cancer

Introduction: Small cell prostate cancer (SCPC) is one of the most common extrapulmonary small cell cancers as well as one of the most common histology type among non-adenocarcinoma prostate cancers. While small cell lung cancer follows a limited-versus-extensive staging system which is different from the stage I to IV system used for non-small cell lung cancer, the prostate adenocarcinoma staging system is used in SCPC despite its distinct clinical feature and aggressive disease course. Limited by the rarity of SCPC, the optimal staging strategy for SCPC remains unknown. The present study aimed to investigate the prognostic value of limited-vs-extensive staging system in SCPC patients. Method: The Surveillance, Epidemiology, and End Results database was used to analyze the incidence and outcome of small cell prostate cancer. Patients diagnosed between the year 2004 through 2015 were included. Limited stage is defined as those without metastasis regardless of degree of local invasion. Extensive stage is defined as any metastasis to locoregional lymph node, to distant lymph node, or to distant organs. Result: A total of 364 SCPC patients are included in the study cohort, accounting for 0.05% of all prostate cancer cases (n=665,054). Age adjusted incidence of SCPC was 0.959 per 1,000,000 per year over the whole study period. The median age at diagnosis of SCPC is 71 years. The median overall survival is 9 months. In the 322 patients with known metastasis status, 243 (75.5%) patients are in extensive stage, whereas 79 patients are in limited stage. Patients in extensive stage are more likely to have PSA level greater than 20 than those in limited stage (26.3% vs 6%), but a similar proportion of patients in both groups have PSA level less than 4 (44.3% vs 40.0%). Compared to patients with extensive stage, those with limited stage disease had a significantly better overall survival (17 months vs 9 months, p Conclusion: SCPC patients can be staged to limited stage and extensive stage based on the absence versus presence of metastasis. T stage in limited stage patient and type of metastasis in extensive stage patient is not associated with different outcome. Citation Format: Salman Syed, Faisal Ali, Spyridon Basourakos, Zimu Gong. Limited-versus-extensive staging system for small cell prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4189.