Neuroendocrine carcinomas (NECs) originating outside the lung are not well understood and are often treated similarly to lung NECs. This approach may overlook crucial distinctions between these two categories of tumors and the diversity within extrapulmonary NECs. A comprehensive Comparative Study is needed to address these gaps in knowledge.
Methods: A Large-Scale Comparative Analysis
This research utilized data from the Surveillance, Epidemiology, and End Results (SEER) program, spanning from 1973 to 2012. This extensive dataset allowed for a detailed comparative analysis to estimate the prevalence of lung NECs versus various extrapulmonary NEC subgroups. The study investigated epidemiological patterns across different locations and calculated median and 5-year overall survival rates for each group.
Key Findings: Disparities in Morphology and Primary Site
Out of 162,983 NEC cases examined, 14,732 were identified as extrapulmonary. Among these extrapulmonary cases, gastrointestinal NECs were the most frequent (37.44%), followed by NECs of unknown primary origin (28.2%), and NECs at other sites (34.4%). A significant comparative finding was the difference in tumor morphology. Lung NECs exhibited predominantly small cell morphology (95.2%), while gastrointestinal NECs showed this morphology in only 38.7% of cases, highlighting substantial heterogeneity across sites.
Epidemiological Variations: Age, Stage, and Demographics
The comparative study revealed significant epidemiological differences. Median age at diagnosis varied considerably across groups (range, 48-74 years). The proportion of cases diagnosed at a distant stage also differed substantially, ranging from 24% to 77%. Furthermore, incidence patterns varied by sex and race, emphasizing the diverse epidemiological profiles of these cancers based on their primary location.
Survival Rate Disparities: Anatomical Site Matters
Survival analysis revealed notable differences. Median survival for lung NEC patients was 7.6 months, and for gastrointestinal NEC patients, it was 7.5 months, with substantial variation within gastrointestinal NECs (25.1 months for small intestine NECs to 5.7 months for pancreatic NECs). Patients with unknown primary NECs had the poorest median survival at 2.5 months. Five-year survival rates for localized disease ranged widely, from 58%-60% for female genital tract and small intestine NECs to a low of 25% for esophageal NECs. Crucially, the primary tumor site remained a statistically significant prognostic factor for survival, even after accounting for other known prognostic variables (P<.0001).
Conclusion: Implications for Prognosis and Treatment
This comprehensive comparative study, the largest of its kind to date, provides critical epidemiological insights into NECs. The findings underscore significant variations in incidence, morphology, and survival based on anatomical site and morphological subtype. These results emphasize that extrapulmonary NECs are not a homogenous group and differ significantly from lung NECs. The study highlights the importance of considering the primary tumor site in prognosis and treatment strategies, suggesting that a curative approach remains a possibility for patients with non-metastatic NECs.
