Diagnostic utility and prognostic performance of a 92-gene cancer classifier to molecularly profile periampullary adenocarcinomas.

Abstract

197 Background: Due to the small anatomic size, multiplicity of epitheliums, and suboptimal diagnostics determining the site of origin of periampullary adenocarcinomas (PAA) is a challenge. We investigated the ability of a 92-gene RT-PCR assay (CancerTYPE ID) to categorize PAA and to prognostically stratify ampullary adenocarcinomas. Methods: 45 PAA patients who underwent pancreaticoduodenectomies were included; samples were histopathologically verified for tumor subtype determination (pancreatic, extrahepatic biliary, ampullary, or duodenal). Blinded FFPE tumor sections underwent molecular testing and were compared for concordance to histopathological tumor types and prognostic performance. 28 of these samples had previously undergone whole-genome RNA profiling (Overman et al. GI ASCO 2011 a161). Results: Molecular classification of 43 (96%) evaluable samples (13 ampullary, 10 pancreatic, 10 biliary, 10 duodenal) showed 91% concordance: ampullary [5 intestinal (int), 7 pancreaticobiliary (pb)], pancreatic [10 pb], duodenal [3 int, 7 gastroesophageal (ge)], biliary [7 pb]. The 92-gene assay was prognostic with a median OS of 70 m for ge/int cases vs. 32 m for pb cases, P=0.05. Discordant classifications were ge for 1 ampullary and 2 biliary samples, and ovary for 1 biliary case. Previous unsupervised RNA hierarchical clustering of all 13 ampullary cases had identified two prognostic groups (a good-prognosis int-like and a poor-prognosis pb-like), which were identical to the 92-gene classification for 12 cases (5 int and 7 pb). These two ampullary subgroups were prognostic with median OS of 63 vs. 24 m, P=0.07, respectively. Conclusions: The 92-gene assay demonstrated diagnostic utility for molecular site-of-origin classification of PAA. These results support exploration of this approach for the management of metastatic PAA (in which pathologic review of a primary resection specimen is not an option). Molecular classification of ampullary adenocarcinomas into intestinal and pancreaticobiliary subgroups is prognostically relevant; these and the gastric-like molecular profile of duodenal adenocarcinomas may have therapeutic implications.