Clinicopathologic Analysis of Pancreatic Adenocarcinoma in African Americans and Caucasians

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Abstract
African Americans have a higher incidence of pancreatic adenocarcinoma than do Caucasians for unknown reasons. Whether other clinicopathologic differences exist between these two groups is not known. This study was undertaken to compare the clinical, pathologic, and biologic findings for a group of patients with a histologic diagnosis of pancreatic ductal adenocarcinoma of the usual type in a single institution. We studied 410 patients (166 African Americans and 244 Caucasians) with a histologic diagnosis of pancreatic ductal adenocarcinoma of the usual type and analyzed (a) the clinicopathologic characteristics of the tumors, (b) the immunohistochemical expression of biomarkers implicated in pancreatic carcinogenesis (Fas, Fas ligand, HER2, p21/waf-1, p27, and p53), and (c) the presence and types of K-ras mutations at codon 12 as determined by polymerase chain reaction–mediated amplification. All elements of data were not available for all patients. African Americans had significantly higher rates of K-ras mutations to valine than did Caucasians (58% versus 22%, respectively;p = 0.015) and were less likely to have received chemotherapy (45% versus 70%, respectively;p = 0.001) or radiation therapy (34% versus 57%, respectively;p = 0.003). African Americans also had more frequent positive surgical margins than did Caucasians (56% versus 25%, respectively;p = 0.001), although mean tumor size was similar between the two groups (African Americans, 3.4 cm; Caucasians, 3.5 cm). Other clinicopathologic variables were similar between the two groups, including median survival (African Americans, 8.5 months; Caucasians, 10.1 months), 5-year survival (African Americans, 3%; Caucasians, 6%), and stage at presentation. Differences in biomarker immunoreactivity included less frequent Fas expression (4% versus 24%, respectively;p = 0.048) and a trend toward more frequent strong HER2 expression (39% versus 18%, respectively p = 0.11) in African Americans than in Caucasians. Although African American and Caucasian patients had similar survival rates associated with usual type pancreatic ductal adenocarcinoma, there were differences in management and expression of biologic markers between these two groups. African Americans were significantly less likely to receive radiation therapy or chemotherapy than were Caucasians, which may assume more importance as treatment improves. At the molecular level, African Americans had more frequent K-ras mutations to valine than did Caucasians.