Liquid biopsies for faster diagnosis of suspected advanced pancreatic and biliary tract cancers: ACCESS, a UK innovation programme.

614 Background: Tissue diagnosis in biliary tract (BTC) and pancreatic (PC) cancer is challenging due to anatomical location and patient (pt) factors (frailty, sepsis); approximately 25% of invasive biopsies are nondiagnostic, requiring repeat procedure. Most BTC and PC pts present with advanced disease. In stage III and IV solid tumours, Guardant 360 (G360) 74 gene panel liquid biopsy (LB) detects ctDNA in 80%/85% of BTC/PC. ACCESS is a real-world innovation programme evaluating the impact of adding G360 to the current invasive diagnostic pathway for suspected BTC/PC in 6 hospitals in West London; (n=240). Methods: This is a pre-planned interim analysis of the first sequential 65 pts with G360 in ACCESS. Patients were age>18 years, ECOG ≤ 2 with high radiographic suspicion of stage III/IV BTC or PC without histological diagnosis at registration or other malignancies within 3 years. Positive LBs were reviewed at molecular tumour board with 4 pre-specified levels of diagnostic certainty: diagnostic/consistent/possibly/not consistent. Tumour board review followed. Endpoints include repeat biopsy rate, change in time to diagnosis, quality of life, health economic assessment and patient satisfaction. Results: 64 patients were analysed (1 excluded). 50% female, median age 73 years (43-94), suspected cancer sites 14%/77%/9% BTC/PC/either BTC or PC. Suspected stage III/IV disease 38%/62%. ctDNA detection rate was 80%/100%/82% in overall cohort/BTC/PC. Most commonly detected LB alterations in suspected BTC/PC were TP53, APC, ATM, CDK/TP53, KRAS, CDKN2A, ARID1A. In BTC and PC, diagnostic method was liquid biopsy alone/liquid and tissue biopsy/tissue alone in 16%/49%/33%. 17% had repeat biopsy. Sensitivity/specificity of cancer diagnosis (all-comers) using liquid biopsy was 86% (95% CI 73.3-94.2)/38.5% (95% CI 13.9-68.4). Conclusions: There is a high ctDNA detection rate with high level diagnostic certainty, promising for future genomic transformation of BTC/PC diagnostic pathways, potentially reducing repeat invasive biopsies, speeding up diagnosis, facilitating precision therapy, with ACCESS defining a blueprint for molecular integration of liquid biopsies. Full recruitment is planned to complete in March 2024.