# Circulating tumor DNA profiling of advanced biliary tract cancers

Source: https://onco.cc/key-papers/paper-mody-biliary-ctdna-profiling-jco-po-2019/  
OnCo record `paper-mody-biliary-ctdna-profiling-jco-po-2019` (Key paper). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Blood tests for tumour DNA found a mutation in three quarters of 124 patients with advanced bile duct or gallbladder cancer and a drug-relevant change in about half, showing the approach is feasible when tissue is hard to get.

## Summary

From January 2015 to February 2018, 124 patients with locally advanced or metastatic biliary tract cancer at the Mayo Clinic underwent circulating tumour DNA testing with a clinically available assay, most (n = 122) on a 73-gene panel; about 70% had intrahepatic disease. 138 samples were included.

Excluding variants of unknown significance, 105 samples (76%) had one or more alterations, with an average of three alterations per sample and a median allelic fraction of 0.52%. Therapeutically relevant alterations were observed in 76 patients (55%), including BRAF mutations, ERBB2 amplifications, FGFR2 fusions, FGFR2 mutations and IDH1 mutations seen in 21% of patients. A different spectrum was observed in patients under 50.

## Fields

- Kind: Key paper
- Last checked: 2026-09-24
- Journal: JCO Precision Oncology
- Year: 2019
- DOI: 10.1200/po.18.00324
- Authors: Mody K, Kasi PM, Yang J, et al.
- Findings: 76% of 138 plasma samples carried at least one alteration; median allelic fraction 0.52%.; Therapeutically relevant alterations in 55% of patients, including ERBB2 amplification, BRAF, FGFR2 and IDH1.; Different alteration spectrum in patients under 50.
- What it means: Biliary tumours are often diagnosed on tiny biopsies or brushings, so a blood-based panel that detects HER2 amplification and other targets in half of patients is a practical route to testing, with tissue confirmation where the blood is uninformative.
- Caveats: Single centre, predominantly intrahepatic; gallbladder cancers were a minority.; Plasma panel (Guardant360) of 73 genes; low allelic fractions mean negatives do not exclude a tissue alteration.

## Sources

- Mody et al., JCO Precis Oncol 2019: circulating tumour DNA profiling of 124 biliary tract cancers: https://doi.org/10.1200/po.18.00324
- PubMed: https://pubmed.ncbi.nlm.nih.gov/35100741/

## Connected records

- cancers: [Biliary tract cancer (all types)](https://onco.cc/cancers/biliary-tract-cancer/), [Biliary tract cancer (cholangiocarcinoma)](https://onco.cc/cancers/cholangiocarcinoma/), [Gallbladder cancer](https://onco.cc/cancers/gallbladder/)
- technologies: [Liquid biopsy (ctDNA)](https://onco.cc/technologies/liquid-biopsy/)
- targets: [BRAF](https://onco.cc/targets/braf/), [FGFR2](https://onco.cc/targets/fgfr2/), [HER2](https://onco.cc/targets/her2/), [IDH1 / IDH2](https://onco.cc/targets/idh/)
- drugs: [Guardant360 CDx](https://onco.cc/drugs/guardant360-cdx/)
- companies: [Guardant Health](https://onco.cc/companies/guardant-health/)
- institutions: [Mayo Clinic](https://onco.cc/institutions/mayo-clinic/)
- terms: [Circulating tumour DNA (ctDNA)](https://onco.cc/terms/ctdna/), [HER2 testing in biliary tract cancer (IHC, ISH and NGS)](https://onco.cc/terms/her2-testing-in-biliary-cancer/)
- journals: [JCO Precision Oncology](https://onco.cc/journals/jco-precision-oncology/)

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