Circulating Tumor DNA (ctDNA) as a Predictive Biomarker for Immunotherapy in Advanced or Locally Advanced dMMR/MSI-H Colorectal Patients

dMMR/MSI-H colorectal cancer patients are the dominant population of immunotherapy/neoadjuvant immunotherapy, but imaging evaluation of immunotherapy efficacy is insufficient. There are some cases, although no disease remission was found on imaging,pathological complete response (pCR) was confirmed after surgery. Meanwhile,previous studies have shown that dynamic changes in ctDNA can help assess immunotherapy efficacy. Therefore, we propose to conduct a multicenter, prospective, observational clinical study to explore the efficacy prediction and monitoring value of ctDNA in immunotherapy for advanced or locally advanced dMMR/MSI-H colorectal cancer.

Inclusion Criteria: \- advanced or locally advanced dMMR/MSI-H colorectal cancer Expected to receive/be receiving immune checkpoint inhibitor therapy ECOG performance score is 0-1, life expectancy ≥12 weeks Exclusion Criteria: \- The presence of other uncured malignancies Patients with one or more serious concomitant systemic diseases that, in the investigator's opinion, impair the patient's ability to complete the study Patients with autoimmune disease are not suitable for PD1 monoclonal antibody therapy