Multiomic molecular comparison of primary versus metastatic pancreatic tumors.

213 Background: Pancreatic cancer metastasizes very early, as evidenced by the fact that > 70% of patients with operable disease ultimately develop metastases. Thus, it is likely that the molecular characteristics of primary pancreatic tumors are similar to metastatic lesions. We compared the frequency of genetic alterations and protein expression from primary vs. metastatic pancreatic tumors, and from metastases from different sites. By focusing on actionable genetic and proteomic information, we sought to explore whether targeted therapies could be tailored to patients at metastatic progression based on primary surgical material. Methods: Next generation DNA sequencing (NGS) data of 208 genes and a limited set of protein markers were analyzed from pancreatic tumors of 431 patients enrolled in the Know Your Tumor initiative. Of the 208 genes tested, mutations in 70 were considered potentially actionable based on preclinical and clinical evidence. We compared 146 primary pancreatic tumors against 285 metastatic lesions, and examined subgroups for liver vs. lung vs. other metastatic lesions. Molecular alterations were compared between independent groups for each gene/protein using Fisher’s exact test. Significance was assessed using a false discovery rate adjusted q-value threshold of 0.05. Results: No differences in the specific mutation or expression pattern were observed between primary vs. metastatic lesions, nor across the site of metastasis after correcting for multiple hypotheses. Even the proportion of actionable alterations (including mutations in the homologous recombination DNA repair pathway) was similar across subgroups. Conclusions: Comparison of the muli-omic profile of primary vs. metastatic pancreatic adenocarcinoma reveals that the molecular architecture is very similar, and that actionable alterations are identified at the same frequency. This is unlike the data observed from other solid tumors, (e.g. colon and breast cancer), in which substantial molecular discordance and heterogeneity exists between primary tumors and metastatic sites, but is consistent with the belief that primary pancreatic cancers metastasize early and thus are molecularly indistinguishable from metastatic lesions.