# Implementing Massive Parallel Sequencing into Biliary Samples Obtained through Endoscopic Retrograde Cholangiopancreatography for Diagnosing Malignant Bile Duct Strictures

## TL;DR

This study explores using massive parallel sequencing on biliary samples to distinguish between benign and malignant bile duct strictures, showing potential for early cancer detection.

## Contribution

The study is the first prospective evaluation of MPS-based assays in biliary samples for diagnosing bile duct strictures.

## Key findings

- MPS detected mutations in TP53, BRAF, CTNNB1, SMAD4, and K-/N-RAS in biliary brush cytology and bile fluid from cholangiocarcinoma patients.
- Variant allele frequencies in bile fluid were lower than in biliary brush cytology samples.
- No pathogenic mutations were found in control patients with gallstones.

## Abstract

Despite advancements in radiologic, laboratory, and pathological evaluations, differentiating between benign and malignant bile duct strictures remains a diagnostic challenge. Recent developments in massive parallel sequencing (MPS) have introduced new opportunities for early cancer detection and management, but these techniques have not yet been rigorously applied to biliary samples. We prospectively evaluated the Oncomine Comprehensive Assay (OCA) and the Oncomine Pan-Cancer Cell-Free Assay (OPCCFA) using biliary brush cytology and bile fluid obtained via endoscopic retrograde cholangiopancreatography from patients with bile duct strictures. The diagnostic performance of MPS testing was assessed and compared to the pathological findings of biliary brush cytology and primary tissue. Mutations in TP53, BRAF, CTNNB1, SMAD4, and K-/N-RAS identified in biliary brush cytology samples were also detected in the corresponding bile fluid samples from patients with extrahepatic cholangiocarcinoma. These mutations were also identified in the bile fluid samples, but with variant allele frequencies lower than those in the corresponding biliary brush cytology samples. In control patients diagnosed with gallstones, neither the biliary brush cytology samples nor the bile fluid samples showed any pathogenic mutations classified as tier 1 or 2. Our study represents a prospective investigation into the role of MPS-based molecular testing in evaluating bile duct strictures. MPS-based molecular testing shows promise in identifying actionable genomic alterations, potentially enabling the stratification of patients for targeted chemotherapeutic treatments. Future research should focus on integrating OCA and OPCCFA testing, as well as similar MPS-based assays, into existing surveillance and management protocols for patients with bile duct strictures.