• Emily Chen, Po Y Yip, Annette Tognela, Geovanny Gandy, Clare Earl, Patrick Tran, and Peey-Sei Kok.
• School of Medicine, Western Sydney University, Sydney, New South Wales, Australia.
• Intern Med J. 2024 Mar 1; 54 (3): 414420414-420.

BackgroundExtrapulmonary small cell carcinomas (EPSCCs) are rare cancers, comprising 0.1-0.4% of all cancers. The scarcity of EPSCC studies has led current treatment strategies to be extrapolated from small cell lung cancer (SCLC), justified by analogous histological and clinical features.AimsWe conducted a retrospective cohort study comparing the outcomes of extensive-stage (ES) SCLC and EPSCC.MethodsPatients diagnosed with ES SCLC or EPSCC between 2010 and 2020 from four hospitals in Sydney were identified. Patients who received active treatment and best supportive care were included. The primary endpoint was overall survival (OS), and secondary endpoints were progression-free survival (PFS) and overall response rates (ORRs).ResultsThree hundred and eighty-four patients were included (43 EPSCC vs. 340 SCLC). EPSCC were of genitourinary (n = 15), unknown primary (n = 13) and gastrointestinal (n = 12) origin. Treatment modalities for EPSCC compared to SCLC included palliative chemotherapy (56% vs 73%), palliative radiotherapy (47% vs 59%) and consolidation chest radiotherapy (10% of SCLC). Overall, median OS was 6.4 versus 7 months for EPSCC versus SCLC respectively, but highest in prostate EPSCC (25.6 months). Of those who received chemotherapy (22 EPSCC vs 233 SCLC), median OS was 10.4 versus 8.4 months (HR OS 0.81, 95% confidence interval (CI): 0.5-1.31, P = 0.38); PFS was 5.4 versus 5.5 months (HR PFS 0.93, 95% CI: 0.58-1.46, P = 0.74) and ORR were 73% versus 68%.ConclusionsEPSCC and SCLC appeared to have comparable OS and treatment outcomes. However, the wide range of OS in EPSCC highlights the need for an improved understanding of its genomics to explore alternative therapeutics.© 2023 The Authors. Internal Medicine Journal published by John Wiley & Sons Australia, Ltd on behalf of Royal Australasian College of Physicians.

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