Abstract A001: Clinical-genomic analysis of KRAS wild-type pancreatic cancer confirms alternative targetable drivers and provides insight for age and risk related clinical stratification

Abstract Approximately 8-10% of pancreatic cancers do not harbor mutations in KRAS. Understanding the unique molecular and clinical features of this subset of pancreatic cancer (PC) is important to guide patient stratification for clinical trials of molecularly targeted agents. To this end we investigated a cohort of 795 PC patients from Dana-Farber Cancer Institute who had undergone somatic genomic characterization with OncoPanel, a targeted next-generation sequencing panel with coverage of more than 400 cancer-associated genes. A total of 9.2% (73/795) of cases in our cohort were KRAS WT. The KRAS WT cohort was statistically enriched for MSI-H PC and acinar cell carcinomas (p = 0.0035, p < 0.0001 respectively). Actionable alterations in alternative MAPK drivers were identified in 44% (32/73) of KRAS WT cases. BRAF alterations accounted for 56% (18/32) of detected alternative MAPK drivers, the majority of which (72%) were Class II which exhibit dimer-dependent constitutive activity. Receptor Tyrosine Kinase (RTK) fusion events in BRAF, NTRK1, NRG1, NTRK3, ROS1, and FGFR2 accounted for 25% (8/32) of detected alternative MAPK drivers in KRAS WT tumors. BRAF in-frame deletions showed increased sensitivity to dual pan-RAF and MEK inhibition in organoid models and one patient with a ROS1 fusion received prolonged clinical benefit from targeted therapy. In addition to alternative MAPK drivers, mutations in GNAS (p = 0.0014) and ARID2 (p = 0.045) were significantly enriched in KRAS WT PC, whereas TP53 mutations were significantly less frequent in KRAS WT cases. Interestingly, although not statistically significant, rates of mutation in the other canonical tumor suppressor genes (CDKN2A, SMAD4) were also lower in KRAS WT PC. Clinically, KRAS Mutant (MUT) PC were associated with a decreased overall survival (OS) compared to the KRAS WT cohort [median OS 17.5 vs 24.0 months, HR 1.38, p = 0.036], however this relationship was no longer significant after accounting for other clinical factors. For patients with KRAS WT PC, those with SMAD4 alterations had a significantly decreased OS (HR 6.24, p < 0.001), whereas presence of TP53 or CDKN2A mutations had no significant impact. Lastly, we found that KRAS WT PC was associated with a younger age of onset. Interestingly, we noted that KRAS WT PC patients with a younger age of onset had tumors with few oncogenic alterations whereas no such association was seen in KRAS MUT patients. Validation of this finding in a separate dataset is required and is currently ongoing. In summary, our clinical and genomic characterization of KRAS WT PC identifies a high prevalence of alternative MAPK drivers that are amenable to targeted therapies. Our cohort also recapitulates the previously reported clinical characteristics of KRAS WT PC and identifies the presence of SMAD4 alterations as significantly associated with decreased overall survival in KRAS WT PC. Additional analysis from multiple sources will be critical to risk stratify these patients further and to validate age-related findings. Citation Format: Harshabad Singh, Rachel B. Keller, Kevin S. Kapner, Julien Dilly, Srivatsan Raghavan, Chen Yuan, Eizabeth Cohen, Michael Tolstorukov, Emma Hill, Elizabeth Andrews, Lauren K. Brais, Annacarolina Da Silva, Kimberly Perez, Douglas A. Rubinson, Benjamin L. Schlechter, Michael H. Rosenthal, Jason L. Hornick, Valentina Nardi, Yvonne Li, Hersh Gupta, Andrew Cherniack, Mathew L. Meyerson, James M. Cleary, Jonathan A. Nowak, Brian M. Wolpin, Andrew A. Aguirre. Clinical-genomic analysis of KRAS wild-type pancreatic cancer confirms alternative targetable drivers and provides insight for age and risk related clinical stratification [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A001.