Frequency and oncologic outcomes of KRAS mutations in circulating tumor DNA of patients with pancreatic ductal adenocarcinoma.

Abstract

636 Background: KRAS genetic alterations have been reported in more than 90% of pancreatic ductal adenocarcinoma (PDAC). The association of KRAS mutation subtypes detected in circulating tumor DNA (ct-DNA) with survival remains unclear. We investigated the rate of liquid biopsy detected KRAS mutation subtypes, and their association with overall survival (OS) in patients with PDAC. Methods: The Foundry software platform was used to retrospectively query a single-institution Electronic Health Records to identify patients with PDAC who underwent ct-DNA liquid biopsy from 2018 to 2023 and extract their oncologic outcomes. Results: Liquid biopsies were performed for 313 patients with PDAC; 58% (n=181) were diagnosed with stage IV disease. The median follow-up was 25 months, with median OS 24 months (95%CI=21-29). Overall, 52% (n=162) tested positive for KRAS mutations. Among patients with metastatic disease at diagnosis (n=181), 66.7% (n= 120) tested positive for KRAS mutations. In contrast, only 31.8% (n= 42) of patients with stage I to III disease at diagnosis (n=132) tested positive. Among patients with metastatic disease, those with KRAS positive disease had significantly shorter OS (median OS 13 vs 27 months, HR=2.7, 95%CI=1.7-4.3, P<0.0001). In patients with non-metastatic disease, the median OS was 28 vs 43 months, respectively (HR=1.7, 95%CI=0.97-2.8, P=0.064). The most frequent KRAS mutation was G12D (n=66, 40.7% of KRAS mutations) followed by G12V (n=58, 35.8%), G12R (n=15, 9.3%), and Q61H (n=10, 6.2%). Among KRAS mutations allelic subtypes, KRAS G12D and Q61 mutations had significantly worse OS with median OS 13 and 10 months respectively (P <0.001). The most frequently co-occurring mutations detected in KRAS positive patients were TP53 (n=126, 77.8%), CDKN2A (n=34, 21%), SMAD4 (n=33, 20.4%), and ARID1A (n=12, 7.4%). Examining the prognostic significance of co-occurring mutations among patients with metastatic disease, only detection of co-occurring CDKN2A mutation was associated with worse OS as compared to patients with KRAS mutations without co-occurring CDKN2A mutations (median OS 8 vs 14 months, HR=2, 95%CI=1.1-3.5, P value=0.015). Conclusions: Detection of KRAS mutation in liquid biopsies of patients with metastatic PDAC is associated with worse OS. KRAS G12D/Q61 alterations detection is associated with worse OS compared to other KRAS mutation subtypes. Ct-DNA detection of co-occurring CDKN2A mutation is associated with worse OS in patients with KRAS positive metastatic disease.