Abstract
BackgroundIn contrast to the well-described epidemiology and behavior of small cell lung carcinoma (SCLC), little is known about extrapulmonary small cell carcinoma (EPSCC).MethodsUsing data from the Surveillance, Epidemiology and End Results (SEER) Program (1992–2010), we calculated age-adjusted incidence rates (IRs), IR ratios (IRRs), annual percent change (APC), relative survival (RS), RS ratios (RSRs), and the respective 95% confidence intervals (95% CI) of SCLC and EPSCC according to primary site. We used the SEER historic stage variable that includes localized (confined to the organ of origin), regional (direct extension to adjacent organ/tissue or regional lymph nodes), and distant (discontinuous metastases) stages and combined localized and regional stages into “limited” stage.ResultsThe incidence of SCLC (IR = 76.3/million person-years; n = 51,959) was 22-times that of EPSCC (IR = 3.5; n = 2,438). Of the EPSCC sites, urinary bladder, prostate, and uterine cervix had the highest incidence (IRs = 0.7-0.8); urinary bladder (IRR = 4.91) and stomach (IRR = 3.46) had the greatest male/female disparities. Distant-to-limited stage site-specific IRRs of EPSCC were significantly elevated for pancreas (IRR = 6.87; P < 0.05), stomach, colon/rectum, ovary, and prostate (IRRs = 1.62-2.42; P < 0.05) and significantly decreased for salivary glands, female breast, uterine cervix, and urinary bladder (IRRs = 0.32-0.46). During 1992–2010, significant changes in IRs were observed for EPSCC overall (APC = 1.58), small cell carcinoma of the urinary bladder (APC = 6.75), SCLC (APC = −2.74) and small cell carcinoma of unknown primary site (APC = −4.34). Three-year RS was significantly more favorable for patients with EPSCC than SCLC for both limited (RSR = 2.06; 95% CI 1.88, 2.26) and distant stages (RSR = 1.55; 95% CI 1.16, 2.07). Among limited stage small cell carcinoma, RS was most favorable for salivary glands, female breast, and uterine cervix (RS = 52-68%), whereas RS for nearly all sites with distant stage disease was <10%.ConclusionEPSCC comprises a heterogeneous group of diseases that appears, at least in part, etiologically distinct from SCLC and is associated with more favorable stage-specific patient survival.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1188-y) contains supplementary material, which is available to authorized users.
Highlights
In contrast to the well-described epidemiology and behavior of small cell lung carcinoma (SCLC), little is known about extrapulmonary small cell carcinoma (EPSCC)
Overall, 55,722 cases of small cell carcinoma were diagnosed among residents of SEER-13 during 1992–2010 (IR = 81.8/million PY)
Among EPSCC, we report the highest incidence for the urinary bladder, a site that may clinically manifest early with hematuria or urinary symptoms, as supported by the more than triple number of cases diagnosed with limited stage than distant stage disease
Summary
In contrast to the well-described epidemiology and behavior of small cell lung carcinoma (SCLC), little is known about extrapulmonary small cell carcinoma (EPSCC). In the broad spectrum of neuroendocrine tumors, small cell carcinomas comprise the less differentiated tumors associated with aggressive behavior [1]. Most of what is known regarding the epidemiology of small cell carcinoma is derived from studies of lung cancer. While population-based epidemiologic studies of neuroendocrine tumors have considered incidence according to anatomic site, most have excluded small cell histology, based on the assumption that these aggressive, highly fatal tumors are etiologically distinct from their well-differentiated counterparts [4,5,6,7]. To gain insight into the etiology and behavior of small cell carcinoma, we comprehensively assessed SCLC and EPSCC incidence and patient survival using population-based data from the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) Program
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