Long-term survivors of pancreatic adenocarcinoma show low rates of genetic alterations in KRAS, TP53 and SMAD4

BACKGROUND: Pancreatic adenocarcinoma (PDAC) is one of the deadliest human malignancies. Although surgery is currently the only effective treatment for PDAC, most patients survive less than 20 months after tumor resection. OBJECTIVE: The primary goal was to investigate alterations in KRAS, TP53, SMAD4 and CDKN2A/p16 in tumors from patients with exceptionally long survival after surgery. METHODS: Tumors from 15 patients with PDAC that survived more than 55 months after surgery ("LS") were analyzed for KRAS, TP53, IDH1, NRAS and BRAF using next-generation sequencing. SMAD4 and CDKN2A/p16 was tested using immunohistochemistry. MGMT promoter methylation was investigated. RESULTS: Tumors from "LS" have a lower prevalence of KRAS and TP53 mutations and had more frequently SMAD4 retained expression, if compared with that of patients died within 24 months from surgery. The survival of patients with wild-type KRAS and TP53 tumors was more than twice longer than that of patients bearing KRAS and TP53 mutations (90.2 vs. 41.1 months). Patients with KRAS wild-type tumors and that retained SMAD4 expression had a survival twice longer than cases with alterations in both genes (83.8 vs. 36.7 months). Eleven tumors (39.3%) showed MGMT methylation. CONCLUSIONS: Our data indicate that absence of KRAS, TP53 and SMAD4 genetic alterations may identify a subset of pancreatic carcinomas with better outcome.