Abstract

We prospectively investigated the feasibility of tumor-informed circulating tumor DNA (ctDNA) for detecting minimal residual disease (MRD) in patients with surgically resected 

biliary tract cancer (BTC). Personalized ctDNA panels were designed based on whole-exome sequencing (WES) of the resected tumor tissue for each patient. 

Two serial blood samples (preoperative and within 6 weeks after surgery) were analyzed. A ctDNA test was considered positive if two or more patient-specific mutations were detected.  Among 18 enrolled patients, 14 were evaluable due to inadequate target variants or surgical inoperability. Preoperative ctDNA positivity tended to be higher in advanced stages and node-positive disease. 

After a median follow-up of 17.4 months, progression-free survival (PFS) at 1 and 2 years was 78.6% and 58.2%, respectively. 

Changes in ctDNA status showed three patterns (negative-to-negative, positive-to-negative, positive-to-positive). There was a trend toward poorer PFS with positive ctDNA both before and after surgery. 

Although limited by the small sample size, results suggest a possible role for tumor-informed ctDNA in detecting MRD in resected BTC and warrant further research.

Purpose

The purpose of this study was to evaluate the feasibility and potential clinical utility of tumor-informed ctDNA for detecting minimal residual disease in patients undergoing surgical resection for biliary tract cancer. 

The authors aimed to determine whether personalized ctDNA analysis could identify MRD and correlate with disease progression following curative surgery.

Results

Study Population and ctDNA Panels

- 18 BTC patients were initially enrolled, but 1 patient was excluded due to inoperability and 3 patients were excluded due to too few tumor variants for panel design. 

 Ultimately, 14 patients were analyzed.

ctDNA Detection Before and After Surgery

- Preoperative ctDNA was positive in 10 out of 14 (71.4%) patients.

- Postoperative ctDNA was positive in 6 out of 12 (50.0%) patients with available samples.

- The observed changes in ctDNA status were:

 √ Negative → Negative: 3 patients (25.0%)

 √ Positive → Negative: 3 patients (25.0%)

 √ Positive → Positive: 6 patients (50.0%)

Correlation With Clinical Features and Outcomes

- There was a trend toward higher preoperative ctDNA positivity in patients with advanced stage (III-IV) and node-positive disease, though not reaching statistical significance.

- Among patients negative for ctDNA preoperatively, no progression was observed.

- Five out of 10 preoperative ctDNA positive patients experienced disease progression.

- Postoperatively, progression occurred in 3 out of 6 ctDNA positive patients versus 1 out of 6 ctDNA negative patients.

  Progression-Free Survival (PFS)

 √ After a median follow-up of 17.4 months, the 1-year PFS was 78.6% and the 2-year PFS was 58.2%.

 √ There was an apparent trend toward worse PFS in patients with positive ctDNA before or after surgery, though sample size limited statistical power. 

Conclusions

This prospective study suggests that tumor-informed ctDNA analysis is feasible in surgically resected biliary tract cancer and has potential utility for detecting minimal residual disease. 

Positive ctDNA status both before and after surgery tended to correlate with poorer clinical outcomes, indicating that ctDNA may serve as a biomarker for residual disease and early progression. 

Given the small cohort size, these findings require validation in larger studies before clinical implementation.