Retrospective review of extra-pulmonary small cell carcinoma and prognostic factors

Extra-pulmonary small cell carcinoma (EPSCC) is a rare cause of malignancy, representing 2.5-5 % of all small cell carcinomas, with an incidence rate of 1000 cases per year in the USA. The purpose of this study is to characterize the location, extent of disease, and survival of patients with EPSCC, and to analyze potential clinical prognostic indicators predicting survival.

A retrospective review of all patients with EPSCC between the years 2000 and 2010 was conducted. Patients included for analysis had pathologic diagnosis of EPSCC, poorly differentiated tumors, and negative chest imaging at diagnosis.

53 patients were included in the analysis. 23 patients (43 %) had limited disease (LD) at diagnosis, and 30 patients (57 %) had extensive disease (ED) at diagnosis. Carcinoma of unknown primary represented the largest proportion of patients (40 %), followed by genitourinary (26 %), gastrointestinal (15 %), head and neck (11 %), gynecologic (6 %), and breast (2 %). The median overall survival (OS) was 4.7 months; 14.5 months for LD, and 3.7 months for ED. Genitourinary EPSCC had the best median OS at 13.1 months, and GI carcinomas had the worst at 1.7 months. On univariate analysis, ED (p = 0.0001), non-genitourinary EPSCC (p = 0.036), and hyponatremia were associated with worse OS (p = 0.0176).

In a cohort of patients with EPSCC, hyponatremia, non-genitourinary EPSCC, and extensive disease were associated with worse OS. Anatomic site predicted survival, which suggests that pathologic heterogeneity between individual tumor sites, including mixed tumor pathology, may affect the prognosis of this rare disease. Future directions for research should include thorough pathologic and genetic profiles.