Histology and stage at presentation among patients with rare pancreatic tumors: An exploratory analysis of the SEER database.

Abstract

e15774 Background: Rare pancreatic tumors account for approximately 15% of all pancreatic cancers (PCs) and 8,300 new cases diagnosed within the United States annually, while 85% of PCs diagnosed are classified as adenocarcinomas. Comparatively little research exists to analyze differences in diagnosis between rare PCs and the more common adenocarcinoma given greater clinical interest in the latter. The purpose of this study was to analyze the relationship between PC histology and stage at presentation with a focus on rare histologies. Methods: This study employed a retrospective cohort model using the NCI’s Surveillance, Epidemiology, and End Results (SEER) 1990-2015 database. We included patients diagnosed with PC aged 18+, with the comparator group being patients diagnosed with adenocarcinoma, and “rare” tumors defined as one of the following histologies: ductal, carcinoid, mucinous adenocarcinoma, and undetermined neoplasm. Stage was dichotomized (locoregional versus distant). Multivariable logistic regression was used to describe the association between tumor histology with initial stage at diagnosis, controlling for patient and tumor characteristics. Results: 90,764 PC patients were analyzed: 66.3% adenocarcinoma, 9.6% ductal carcinomas, 4.5% carcinoid, 3.8% mucinous, and 15.8% undetermined neoplasm. 54.7% of all cases were distantly metastasized at diagnosis. In multivariable analysis, pancreatic cancer patients with mucinous histology had greater odds of presenting at late-stage compared to those with adenocarcinoma: OR = 1.41, 95% CI = [1.31, 1.52]. Carcinoid and undetermined neoplasm odds for late stage presentation were not significant compared to adenocarcinoma: OR = 0.99, 95% CI = [0.92, 1.07] and OR = 1.01, 95% Cl = [0.97, 1.05] respectively. Ductal carcinoma was less likely than adenocarcinoma to present with late stage: OR = 0.38, CI = [0.36, 0.40]. Conclusions: We observed that mucinous histology had greater odds of late-stage diagnosis compared to those with adenocarcinoma. Patients with ductal carcinoma was less likely than those with adenocarcinoma to present with late stage. Further investigation is needed to explore the reasons for these differences.