P360 Liquid biopsy to support tissue-free diagnosis and treatment of suspected advanced biliary tract cancer – an access programme case report

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Introduction Biliary tract cancers (BTC) can be challenging to histologically diagnose if there are patient factors precluding biopsy or insufficient tissue for analysis. Guardant 360© liquid biopsy (LB) is CE marked for stage III and IV solid tumors; it detects ctDNA in 80%-95% of BTC. The ACCESS innovation programme is implementing LB in the diagnostic pathway for patients with radiographically suspected stage III or IV BTC or pancreatic cancer (PC). A LB supplemented pathway may reduce the need for repeat biopsy and speed up time to diagnosis. Methods Case report of a patient with suspected advanced BTC enrolled on the ACCESS program. Inclusion criteria are age ≥18 years, ECOG ≤2, radiographic suspicion of stage III/IV BTC or PC with no histological cancer diagnosis. Patients with history of other malignancies within 3 years are excluded. LB results are reviewed by molecular tumor board (MTB) with pre-specified levels of diagnostic certainty: diagnostic/consistent/possibly/not consistent. If LB is deemed diagnostic or consistent patients can enrol on PREVAIL-2 (NCT04566614) which allows for systemic anticancer therapy based on LB alone. Results A 65-year-old patient presented with weight loss and abnormal liver function tests, CT showed a suspected stage 4 BTC, diagnostic workup on the standard of care pathway involved 4 invasive biopsies in a 6-month timeframe, which were all non-diagnostic. The patient was enrolled on ACCESS. LB turnaround time was 18 days and found a NRAS G12D alteration with 0.07% variant allele frequency which was deemed consistent with BTC by MTB. Multidisciplinary tumor board review followed, the patient was enrolled in the PREVAIL-2 clinical trial and was treated with gemcitabine and carboplatin; they had disease regression on CT after 4 cycles. Conclusions This patient had suspected BTC and multiple non-diagnostic invasive procedures over a prolonged period. LB-based diagnosis was made quickly and with high degree of certainty which allowed for chemotherapy treatment without pathological verification on a clinical trial. The patient had a favorable response to chemotherapy that they would not have been able to access otherwise, demonstrating the value of a LB supplemented pathway.

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