Active surveillance after immunotherapy for MMR-deficient colorectal and GI cancers

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This is an observational, multicenter program with two parts: a registry of non-metastatic MMRd/MSI-H GI cancers (prospective and retrospective data) and a Surveillance Study examining non-operative management after complete clinical response to immune checkpoint inhibitors. Part A collects real-world data from patients undergoing surgery or following immunotherapy to understand outcomes across settings. Part B follows patients who achieve complete response on immunotherapy to evaluate relapse-free survival with active surveillance. The study aims to inform whether surgery can be safely avoided in select patients while monitoring long-term oncologic outcomes. Eligibility includes adults with non-metastatic MMRd/MSI-H gastroesophageal, colon, or rectal cancers treated with ICI as first-line therapy.

Why it matters

Who can join: the full rules

Inclusion Criteria:

Part A and Part B:

* Consent and Capacity:
* Participant is 18 years of age or older.
* Participant is legally competent and able to provide informed consent.
* Participant has provided the appropriate written consent
* Diagnosis: Histologically confirmed gastro-oesophageal, colon or rectum cancer, showing mismatch repair-deficiency (MMRd) by immunohistochemistry (loss of immunoreactivity for at least one of the following proteins: MLH1, PMS2, MSH2 and/or MSH6).
* Clinical Stage: Non-metastatic, locally advanced disease, defined as:
* cT2-T4, cN0-2, cM0 for gastro-oesophageal or rectum cancer
* cT4 and/or cN+, cM0 for colon cancer
* Therapy with immune checkpoint inhibitor (ICI) as primary treatment, either:
* Combination ICI therapy (e.g., anti-PD-1 plus anti-CTLA-4 such as nivolumab + ipilimumab) or
* Single-agent ICI therapy (e.g., pembrolizumab, atezolizumab, or other anti- PD(L)1 agents)

Part B only:

* Patient consents to participate in surveillance study
* Complete or near complete response (\*) to primary ICI treatment, as determined by local multidisciplinary team (MDT) assessment, based on restaging 8 weeks after termination of the ICI treatment:
* Radiological imaging (CT/MRI/PET-CT),
* Endoscopic findings, and
* Clinical parameters (e.g., normalization of tumor markers, absence of symptoms \*\*)

  * Note: in case of near complete response up to a total of 12 months of ICI is allowed following multidisciplinary team (MDT) discussion. After diagnosis of a near-complete response, tumor reassessments should be performed every 3 months up to a total treatment period of 12 months. If a complete tumor response is observed within the 12-month period, it should be recorded as the best overall response.

    * Note: Assessment of complete or near complete response does not incorporate ctDNA test results

Exclusion Criteria:

* Recurrent Disease: Known history of previously treated gastrointestinal cancer with recurrence at time of inclusion.
* Metastatic Disease: Evidence of distant metastases (M1) at any point prior to or during ICI therapy.
* Other Malignancies: Active second malignancy (excluding non-melanoma skiN cancer or in-situ cervical carcinoma) that may interfere with study outcomes or surveillance.

Part B only:

* Inadequate response to ICI: Patients with progressive disease, stable disease, or partial response deemed unsuitable for non-operative management.
* Prior Treatment: Any prior systemic therapy, radiotherapy or surgery for the current colon cancer diagnosis before ICI treatment (except biopsy)
* Medical or Psychiatric Conditions: Significant comorbid conditions or psychiatric illness that, in the opinion of the investigator, would impair the patient's ability to comply with protocol requirements, including surveillance.
* Logistical Barriers: Social, geographic, or organizational factors (e.g., lack of access to regular follow-up care, inability to attend surveillance visits) that would prevent adherence to the active surveillance protocol.

Where it's running

• Universitätsspital Basel
  Basel, Switzerland Recruiting
• Spitalzentrum Biel
  Biel, Switzerland Recruiting
• Luzerner Kantonsspital
  Lucerne, Switzerland Recruiting

Study contacts

• Study coordinator: Dieter Köberle, Prof. Dr. med.
• Email: dieter.koeberle@claraspital.ch
• Phone: +41 61 685 85 85

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.