The goal of this clinical trial is to learn about Fruquintinib combined with Adebrelimab and high and low dose radiotherapy in the treatment of second-line and above failure MSS(microsatellite stability) metastatic colorectal cancer.

The main question it aims to answer is: The efficacy and safety of Fruquintinib combined with Adebrelimab and high and low dose radiotherapy in the third line and beyond treatment of MSS metastatic colorectal cancer.

Participants will receive the combination of Fruquintinib and Adebrelimab within 3 weeks after completion of high and low dose radiotherapy on metastases until disease progression or intolerable toxicity occurred.

Inclusion Criteria:

1. Age ≥ 18 years old, gender not limited；
2. Eastern Cooperative Oncology Group (ECOG) performance status (PS) score 0-1；
3. Previously identified as MSS type mCRC；
4. Metastatic colorectal cancer (mCRC) with disease progression after receiving standard second-line treatment according to Chinese Society of Clinical Oncology ( CSCO) guidelines；
5. At least one measurable lesion (RECIST 1.1)；
6. Be able to adhere to the protocol during the research period；
7. Sign the informed consent form.

Exclusion Criteria:

1. For individuals with a history of uncontrolled epilepsy, central nervous system disorders, or mental disorders, the clinical severity of which may hinder the signing of informed consent forms or affect the patient's adherence to oral medication, as determined by the researcher；
2. Accompanied by other malignant tumors that have not been cured；
3. The baseline blood routine and biochemical indicators of the subject do not meet the following criteria: hemoglobin ≥ 90g/L; Absolute neutrophil count (ANC) ≥ 1.5 × 109/L; Platelets ≥ 100 × 109/L; Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) ≤ 2.5 times the normal upper limit; Alkaline phosphatase (ALP) ≤ 2.5 times the normal upper limit value; Serum total bilirubin<1.5 times the normal upper limit value; Serum creatinine<1 times the upper limit of normal; Serum albumin ≥ 30g/L；
4. Serious (i.e. active) heart disease in clinical practice, such as symptomatic coronary heart disease, congestive heart failure, or severe arrhythmia requiring medication intervention, or a history of myocardial infarction in the past 12 months；
5. Irreversible coagulation dysfunction or concurrent active massive bleeding；
6. Combination of active infections requiring antibiotic treatment；
7. Individuals who are allergic to any research drug ingredients；
8. Women with concurrent pregnancy or lactation；
9. Organ transplantation requires immunosuppressive therapy and long-term hormone therapy；
10. Patients with autoimmune diseases；
11. There is a history of drug treatment in previous plans。