Data from Oncogenic drivers and therapeutic vulnerabilities in KRAS wild-type pancreatic cancer

AbstractPurpose: Approximately 8-10% of pancreatic ductal adenocarcinomas (PDAC) do not harbor mutations in KRAS. Understanding the unique molecular and clinical features of this subset of pancreatic cancer is important to guide patient stratification for clinical trials of molecularly targeted agents. Experimental Design: We analyzed a single-institution cohort of 795 exocrine pancreatic cancer cases (including 785 PDAC cases) with a targeted multi-gene sequencing panel and identified 73 patients (9.2%) with KRAS wild-type (WT) pancreatic cancer. Results: Overall, 43.8% (32/73) of KRAS WT cases had evidence of an alternative driver of the mitogen activated kinase (MAPK) pathway, including BRAF mutations and in-frame deletions and receptor-tyrosine kinase (RTK) fusions. Conversely, 56.2% of cases did not harbor a clear MAPK driver alteration, but 29.3% of these MAPK-negative KRAS WT cases (12/41) demonstrated activating alterations in other oncogenic drivers such as GNAS, MYC, PIK3CA and CTNNB1. We demonstrate potent efficacy of pan-RAF and MEK inhibition in patient-derived organoid (PDO) models carrying BRAF in-frame deletions. Moreover, we demonstrate durable clinical benefit of targeted therapy in a patient harboring a KRAS WT tumor with a ROS1fusion. Clinically, patients with KRAS WT tumors were significantly younger in age of onset (Median Age: 62.6 vs. 65.7 years , p = 0.037). SMAD4 mutations were associated with a particularly poor prognosis in KRAS WT cases. Conclusions: This study defines the genomic underpinnings of KRAS WT pancreatic cancer and highlights potential therapeutic avenues for future investigation in molecularly directed clinical trials.