The Endoscopic Ultrasound Molecular Analysis of Pancreatic Cancer (EUMEPC) study.

751 Background: Pancreatic cancer carries a dismal prognosis and limited treatment options. Attempts to implement precision therapies have proved difficult to date, in part due to challenges obtaining high quality genetic material from pancreatic biopsies. Endoscopic ultrasound (EUS) is a common diagnostic procedure, but limited data is available on the clinical utility of these biopsies for comprehensive molecular profiling (CMP) to inform therapeutic choices. Methods: This study aimed to enrol up to 150 patients undergoing EUS biopsies for pancreatic cancer, in order to complete targeted DNA/RNA sequencing on 100. The primary outcome was to characterise the proportion of patients able to undergo CMP on their diagnostic EUS biopsies, with fresh-frozen biopsies preferred but FFPE specimens accepted if there was no alternative. Secondary endpoints included the proportion of patients with clinically relevant molecular findings as determined by Molecular Tumour Board (MTB) discussion, proportion of patients initiating targeted therapies, and quantitative/qualitative analysis on molecular material derived from fresh-frozen versus FFPE EUS biopsies. Results: 109 patients have been enrolled since May 2020, and molecular profiling has been completed for 102 patients. 2 patients (1.8%) were excluded due to having no available biopsies, and 5 biopsies (4.7%) were unable to be sequenced due to inadequate quality metrics. Common oncogenes were detected at roughly expected frequencies, with mutations in KRAS occurring in 91 (89.2%), TP53 in 67 (65.7%), SMAD4 in 11 (10.8%) and CDKN2A in 7 (6.8%). Median tumour mutation burden (TMB) in this cohort was low at 3.1Mut/Mb although 7 patients (6.9%) had a high TMB (defined as >10Mut/Mb), of which 3 (2.9%) had markedly hypermutated tumours (>200Mut/Mb). All processed samples were microsatellite stable. Therapeutically relevant mutations were detected in 21 (20.6%) including RNF43 in 7 patients (6.9%), KRAS G12C and BRCA in 3 patients each (2.9%), in addition to BRAF V600E in 2 (1.9%), and CHEK2 and BARD1 mutations in 1 each (0.9%). High TMB was observed in 7 patients (6.9%). To date, 5 patients (4.9%) have commenced on targeted therapies, with one patient notably experiencing a complete response to targeted therapy which has now been sustained for >12 months. Conclusions: This real-world study confirms the utility of endoscopic biopsies as a valuable and reliable source of genetic material for clinically relevant molecular tumour profiling. Secondary analyses are underway to further characterise treatment and survival implications in this cohort.