Very Long-term Survival Following Resection for Pancreatic Cancer Is Not Explained by Commonly Mutated Genes: Results of Whole-Exome Sequencing Analysis

Abstract

Purpose: The median survival following surgical resection of pancreatic ductal adenocarcinoma (PDAC) is currently <20 months. However, survival ≥10 years is achieved by a small subset of patients who are defined as very long-term survivors (VLTS). The goal of this study was to determine whether specific genetic alterations in resected PDACs determined very long-term survival.

Experimental design: We sequenced the exomes of eight PDACs from patients who survived ≥10 years. On the basis of the results of the exomic analysis, targeted sequencing of selected genes was performed in a series of 27 additional PDACs from VLTSs.

Results: KRAS mutations were identified in 33 of 35 cancers (94%) from VLTSs and represented the most prevalent alteration in our cohort. TP53, SMAD4, and CDKN2A mutations occurred in 69%, 26%, and 17%, respectively. Mutations in RNF43, which have been previously associated with intraductal papillary mucinous neoplasms, were identified in four of the 35 cancers (11%). Taken together, our data show no difference in somatic mutations in carcinomas from VLTSs compared with available data from PDACs unselected for survival. Comparison of clinicopathologic features between VLTSs and a matching control group demonstrated that younger age, earlier stage, well/moderate grade of differentiation, and negative resection margins were associated with VLTS. However, more advanced stage, poor grade, or nodal disease did not preclude long-term survival.

Conclusions: Our results suggest that in most patients, somatic mutations in commonly mutated genes are unlikely to be the primary determinant of very long-term survival following surgical resection of PDAC.