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

Abstract

4133 Background: Due to the small anatomic size, multiplicity of epitheliums, and suboptimal diagnostics determining the site of origin of 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: 171 PAA patients who underwent pancreaticoduodenectomies were included; samples were histopathologically verified for tumor subtype determination: pancreatic (PAN), extrahepatic biliary (EB), ampullary (AMP), or duodenal (DOUD). Blinded FFPE tumor sections underwent molecular testing. Analytical sets were an initial 45 PAA set evaluating concordance to histopathological tumor types and prognostic performance, and a second set of 126 AMP and DOUD adenocarcinoma for validation of prognostic performance. Results: Of the initial 45 patient cohort, molecular classification of 43 (96%) evaluable samples (13 AMP, 10 PAN, 10 EB, 10 DOUD) showed 91% concordance: AMP [5 intestinal (int), 7 pancreaticobiliary (pb)], PAN [10 pb], DOUD [3 int, 7 gastroesophageal (ge)], EB [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 AMP and 2 EB samples, and ovary for 1 EB case. Previous unsupervised RNA hierarchical clustering (Overman GI ASCO 2011 a161) of all 13 AMP 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 of the 13 cases. Conclusions: In the initial cohort of 45 patients, the 92-gene assay demonstrated diagnostic utility for molecular site-of-origin classification of PAA; evaluation of the remaining 126 ampullary and duodenal cases will be presented. 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.