Rare subtypes of pancreatic cancer: Clinical outcomes and implications for clinical trial enrollment.

Abstract

445 Background: Pancreatic cancer subtypes such as adenosquamous (AS) and squamous cell carcinoma (SCC) are rare and poorly understood. Treatment recommendations are extrapolated from pancreatic adenocarcinoma (AC) and these patients are often included in AC clinical trials. Herein, we describe clinical outcomes and inclusion of these subtypes in AC clinical trials. Methods: The National Cancer Database (NCDB) was queried to identify patients with AC, AS, and SCC between 2004 and 2014. Overall survival was evaluated using Kaplan-Meier methodology and multivariable (MVA) cox regression models were fit to identify differences in survival outcomes between subtypes adjusted by baseline demographic and clinical variables. ClinicalTrials.gov was interrogated to identify inclusion of AS and/or SCC in contemporary PA clinical trials. Results: We identified 115,061 patients with pancreatic cancer. Median age was 69 (range 18 – 90) and median follow up was 54 months (95% CI 53 – 55). Age, sex, median income, education, comorbidities, race, and stage were significantly associated with overall survival (OS). OS by subtype compared to AC: AS HR of 0.98 (p = 0.59) and SCC HR 1.29 (p < 0.001). OS by subtype and stage compared to AC: stage I/II, AS HR of 0.98 (p = 0.59), SCC HR 1.44 (p = 0.001); stage III, AS HR of 1.32 (p = 0.02) and SCC HR 1.48 (p = 0.01); stage IV, AS HR of 1.1 (p = 0.06), SCC HR 1.2 (p = 0.06). Data from 283 phase II or III interventional trials completed between 2008-2018 were exported from clinicaltrials.gov. The majority of trials listed did not specify inclusion or exclusion of AS or SCC subtypes. Conclusions: This is the largest report of clinical outcomes in rare subtypes of pancreatic cancer. SCC and to a lesser extent, AS, have worse OS compared to AC. It is unclear how rare pancreatic cancer subtypes are handled in the inclusion and analysis of clinical trial data and how this may impact enrollment and survival outcomes.[Table: see text]