415 Patients With Adenosquamous Carcinoma Of The Pancreas: A Population-Based Analysis Of Prognosis and Survival

Abstract

Introduction: Adenosquamous carcinoma is a rare cancer of the pancreas, accounting for approximately 1-4% of exocrine pancreatic malignancies. Because of the uncommon nature of this tumor, our understanding of the disease and its prognosis comes mainly from small retrospective studies and case reports. Methods: Using Surveillance, Epidemiology, and End Results (SEER) database (1988 to 2007), we identified all patients with a diagnosis of adenosquamous or adenocarcinoma of the pancreas. The demographic factors, tumor characteristics, resection status, and long-term survival were compared between the groups. Results: A total of 415 patients with pancreatic adenosquamous carcinoma and 45,693 patients with adenocarcinoma were identified. The gender and race distributions were similar in the two groups. When compared to patients with adenocarcinoma, patients with adenosquamous carcinoma were less likely to have disease located in the head (44.6% vs 53.5%, P<0.0001) and more likely to have disease in the body or tail of the pancreas (29.2% vs 19%, P<0.0001). The stage distribution was similar between the two groups with approximately 60% of patients in each group presenting with distant or unstaged disease. In cancers where differentiation status was known, adenosquamous carcinoma (N=241) was poorly differentiated in 71% of cases while adenocarcinoma (N=24,796) was poorly differentiated in 45% of cases (P<0.0001) Overall, 35% of patients with locoregional adenosquamous carcinoma or adenocarcinoma were considered resectable. In patients with locoregional disease, resection increased over time from 26% in 1988 to 56% in 2007. Patients with locoregional adenosquamous carcinoma were more likely to be resected than patients with locoregional adenocarcinoma (56.3% vs. 47.4%, P=0.02). The 2-year survival was 11% in both groups (P=NS). However, following resection, patients with adenosquamous carcinoma had worse 2-year survival (29% vs. 36%, P<0.0001). In a multivariate analysis of patients with adenosquamous carcinoma, resection was the only independent predictor of survival for patients with locoregional disease, with unresected patients being 2.35 times more likely to die (HR = 2.35, 95% CI=1.47-3.76). Conclusions: Our study is the first population-based study to evaluate outcomes in patients with adenosquamous carcinoma of the pancreas. Patients with adenosquamous carcinoma present at a similar stage to those with pancreatic adenocarcinoma, but have tumors that are more likely to occur in the pancreatic tail and are more often poorly differentiated. Consistent with previous small studies, our population-based study demonstrates that the long-term survival following surgical resection for patients with adenosquamous carcinoma of the pancreas is significantly worse when compared to patients with adenocarcinoma; however, patients with adenosquamous carcinoma can still benefit from surgical resection.