ctDNA-Guided Immunotherapy for dMMR/MSI-H Colon Cancer

September 24, 2026 updated by: Junjie Peng, Fudan University

A Single-Arm Phase II Study of Circulating Tumor DNA-Guided Neoadjuvant Immunotherapy for dMMR/MSI-H Colon Cancer

This prospective, multicenter, single-arm phase II interventional study evaluates whether longitudinal circulating tumor DNA (ctDNA) monitoring can guide neoadjuvant immunotherapy and surgical decision-making in dMMR/MSI-H colon cancer. Participants with ctDNA clearance proceed to curative surgery, whereas those with persistent ctDNA positivity escalate to combined PD-1 and CTLA-4 inhibitor therapy.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This prospective, multicenter, single-arm phase II study evaluates the clinical utility of longitudinal circulating tumor DNA (ctDNA) monitoring to guide neoadjuvant immunotherapy and surgical decision-making in patients with dMMR/MSI-H colon cancer.

Eligible participants will initially receive neoadjuvant PD-1 inhibitor monotherapy. Peripheral-blood ctDNA will be assessed at baseline and after 3 to 4 treatment cycles. Participants with ctDNA clearance will proceed to curative surgery. Participants with persistent ctDNA positivity will be considered to have potential resistance to PD-1 inhibitor monotherapy and will escalate to combined PD-1 and CTLA-4 inhibitor therapy. ctDNA will be reassessed every 2 cycles during combination therapy. Participants will undergo curative surgery after ctDNA clearance or after no more than 4 cycles of combination treatment, regardless of final ctDNA status.

All participants will undergo postoperative ctDNA/minimal residual disease (MRD) testing 1 month after surgery. The study will evaluate pathological response, survival outcomes, the concordance of ctDNA with pathological and imaging assessments, and treatment- and surgery-related safety.

Study Type

Interventional

Enrollment (Estimated)

23

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • China
      • Shanghai, China, 200000
        • Recruiting
        • Fudan University Shanghai Cancer Center
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 75 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Written informed consent obtained before any study-related procedures.
  • Age 18 to 75 years, inclusive.
  • Histologically confirmed colon adenocarcinoma, mucinous adenocarcinoma, or signet-ring cell carcinoma, with the tumor located at least 15 cm from the anal verge.
  • dMMR/MSI-H status confirmed by immunohistochemistry, polymerase chain reaction, or next-generation sequencing.
  • Eastern Cooperative Oncology Group performance status of 0 or 1 and an expected survival of at least 3 months.
  • Adequate hematologic, hepatic, renal, coagulation, thyroid, and cardiac function, as defined in the protocol.
  • Negative pregnancy test for women of childbearing potential; agreement to use highly effective contraception, when applicable.

Exclusion Criteria:

  • Prior treatment with a PD-1 inhibitor, CTLA-4 inhibitor, or other immunotherapy.
  • Symptomatic or high-risk bowel obstruction, bleeding, perforation, pneumonitis, or other conditions that may compromise safe study participation.
  • Another malignancy diagnosed within 5 years before the first study treatment, except for specified definitively treated low-risk malignancies.
  • Current participation in another interventional clinical study, or receipt of another investigational drug or investigational device within 4 weeks before the first study treatment.
  • Active autoimmune disease requiring systemic treatment within 2 years before the first study treatment, or recent systemic corticosteroid or other immunosuppressive therapy.
  • Uncontrolled pleural effusion or ascites, prior allogeneic organ transplantation (except corneal transplantation), or allogeneic hematopoietic stem cell transplantation.
  • Known hypersensitivity to any study drug component.
  • Toxicities or complications from prior treatment not recovered to Grade 1 or baseline, except for specified conditions.
  • HIV infection, untreated active hepatitis B infection, or active hepatitis C infection.
  • Receipt of a live vaccine within 30 days before the first study treatment.
  • Pregnancy or breastfeeding.
  • Any serious or uncontrolled systemic disease, active infection, clinically significant laboratory abnormality, or other condition that may interfere with study participation or place the participant at unacceptable risk, as judged by the investigator.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: ctDNA-Guided Neoadjuvant Immunotherapy |

Participants receive PD-1 inhibitor monotherapy. ctDNA testing after 3-4 cycles determines whether they proceed to curative surgery or escalate to PD-1 plus CTLA-4 inhibitor therapy; all participants subsequently undergo curative surgery.
Drug: PD-1 inhibitor

200 mg intravenously on Day 1 of each 3-week cycle. All participants receive initial monotherapy.

Drug: CTLA-4 inhibitor

1 mg/kg intravenously on Day 1 of each 3-week cycle. Administered with the PD-1 inhibitor only to participants with persistent ctDNA positivity after 3-4 cycles of monotherapy.

Diagnostic test: ctDNA/MRD testing

Peripheral-blood ctDNA testing at baseline and after 3-4 cycles of monotherapy; every 2 cycles during combination therapy, when applicable; and 1 month after surgery.

Procedure: Curative Surgery

Curative surgery after ctDNA clearance or after no more than 4 cycles of combination treatment.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Pathological Complete Response Rate
Time Frame: At curative surgery, following completion of neoadjuvant therapy

Pathological assessment of the surgical resection specimen; pCR is defined as no residual viable cancer cells after treatment (ypT0N0M0).
At curative surgery, following completion of neoadjuvant therapy

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Major Pathological Response Rate
Time Frame: At curative surgery, following completion of neoadjuvant therapy

Pathological assessment of the surgical resection specimen; MPR is defined as residual viable tumor cells ≤10%.
At curative surgery, following completion of neoadjuvant therapy
3-Year Event-Free Survival
Time Frame: From enrollment up to 3 years

Time from enrollment to first radiographic disease progression or death, whichever occurs first.
From enrollment up to 3 years
3-Year Overall Survival
Time Frame: From enrollment up to 3 years

Time from enrollment to death from any cause.
From enrollment up to 3 years
Concordance of ctDNA Status With Pathological Complete Response
Time Frame: After 3-4 cycles of PD-1 inhibitor monotherapy (21-day cycles) and at curative surgery; for persistent ctDNA positivity, every 2 cycles of PD-1 plus CTLA-4 inhibitor therapy (21-day cycles; up to 4 cycles).

Preoperative ctDNA status will be compared with postoperative pathological complete response results.
After 3-4 cycles of PD-1 inhibitor monotherapy (21-day cycles) and at curative surgery; for persistent ctDNA positivity, every 2 cycles of PD-1 plus CTLA-4 inhibitor therapy (21-day cycles; up to 4 cycles).
Concordance Between ctDNA Dynamics and Imaging Assessment
Time Frame: Baseline through curative surgery, up to 24 weeks (each cycle is 21 days).

ctDNA positivity, clearance, and dynamic changes will be compared with RECIST version 1.1 imaging response assessments.
Baseline through curative surgery, up to 24 weeks (each cycle is 21 days).
Number of Participants With Treatment-Emergent Adverse Events, as Assessed by CTCAE v5.0
Time Frame: From first dose through 30 days after the last dose.

Number and proportion of participants with at least one treatment-emergent adverse event, including treatment-related and immune-related adverse events.
From first dose through 30 days after the last dose.
Number of Participants With Grade 3 or Higher Treatment-Related Adverse Events, as Assessed by CTCAE v5.0
Time Frame: From first dose through 30 days after the last dose.

Number and proportion of participants with at least one Grade 3 or higher treatment-related adverse event.
From first dose through 30 days after the last dose.
Number of Participants With Serious Adverse Events
Time Frame: From first dose through 90 days after the last dose.

Number and proportion of participants with at least one serious adverse event.
From first dose through 90 days after the last dose.
Number of Participants With Treatment-Related Delay of Curative Surgery
Time Frame: From first dose through curative surgery up to 24 weeks

Number and proportion of participants whose curative surgery is delayed because of treatment-related toxicity, as determined by the investigator.
From first dose through curative surgery up to 24 weeks

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Fudan University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

September 14, 2026

Primary Completion (Estimated)

December 31, 2027

Study Completion (Estimated)

December 31, 2030

Study Registration Dates

First Submitted

September 12, 2026

First Submitted That Met QC Criteria

September 24, 2026

First Posted (Actual)

September 25, 2026

Study Record Updates

Last Update Posted (Actual)

September 25, 2026

Last Update Submitted That Met QC Criteria

September 24, 2026

Last Verified

September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Neo-ctDNA-Colon

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data, including de-identified data, will not be made available to external researchers. Study data will be processed and stored within China. Aggregate results may be published without identifiable participant information.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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