Use of gene expression analysis of periampullary carcinomas to identify biliary-like and intestinal-like subgroups of ampullary and duodenal carcinomas.
161 Background: Though adenocarcinomas of the ampulla of Vater are classified as biliary cancers, the epithelium of origin and treatment approach for these rare tumors remains controversial. We compared the gene expression profiles of ampullary carcinomas with that of known periampullary carcinomas. Methods: We analyzed 32 fresh-frozen resected untreated periampullary carcinomas (8 pancreatic, 2 extrahepatic biliary, 8 non-ampullary duodenal, and 14 ampullary) with verified histology and >70% tumor tissue using the Affymetrix U133 Plus 2.0 genome array. Hierarchical clustering of all samples based upon pancreatic and duodenal differentially expressed genes and unsupervised hierarchical clustering was done. Ampullary and duodenal samples were analyzed for histologic subtype (pancreaticobiliary, intestinal, mixed), MSI by PCR, CDX-2 by IHC and KRAS and PI3K mutations by mass spectroscopy-based sequencing (Sequenom). Results: We identified 3 subgroups: pancreatic (8 pancreatic, 1 duodenal), biliary-like (4 duodenal, 7 ampullary, 2 biliary) and intestinal-like (3 duodenal, 7 ampullary). The intestinal-like subgroup had a significantly improved RFS (p=0.03) and OS (p =0.04) compared to the biliary-like subgroup, after stratification by grade and stage. Unsupervised clustering of only ampullary and duodenal samples identified very similar good prognostic (4 duodenal, 5 ampullary) and bad prognostic groups (3 duodenal, 9 ampullary) with 3-year RFS 75% vs. 31%, p =0.05 and 3-year OS 100% vs. 27%, p =0.01. These 2 groups showed no statistically significant differences in adenoma (56% vs 25%), poor differentiation (11% vs 42%), T4 (33% vs 25%), N1 (67% vs 100%), MSI-high (22% vs 0%), KRAS mutations (33% vs 17%), or PI3K mutations (0% vs 17%). CDX-2 expression (100% vs 50%, p=.04) and intestinal histologic subtype (100% vs 0%, p <0.01) were more common in the good prognostic group. Conclusions: Gene expression analysis classifies ampullary carcinomas with duodenal carcinomas and identifies a good prognosis intestinal-like group and a poor prognosis biliary-like group. These findings have therapeutic implications. [Table: see text]