Intestinal Low Dose Radiotherapy Combined With Immunotherapy in Immune-resistant Metastatic Malignant Solid Tumors

Inclusion criteria

• Age ≥18 years, ≤80 years, regardless of gender.
• ECOG level 0-2.
• Expected life span>3 months.
• At least one accessible and measurable lesion should be selected as the target lesion for observation according to RECIST criteria.
• Patients with metastatic solid tumors (of any histology) without standard therapy options, who have previously received immunotherapy, immunotherapy combined with chemotherapy, or immunotherapy combined with anti-angiogenesis treatment and have shown disease progression.
• Patients should not be considered eligible for surgical treatment.
• Patients with brain metastases that are assessed as clinically stable after treatment through repeated CT and/or MRI scans are eligible.
• Patients have complete clinical and pathological information.
• Patients should not be borthered by any psychological, family, social or geographical conditions that may hinder compliance with the research protocol.
• Patients should be able to understand the informed consent form, voluntarily participate, and sign the informed consent form.
• Other indicators accord with the general inclusion criteria for clinical trials.

Exclusion criteria

• Patients with contraindications to radiation therapy and immunotherapy.
• Previous occurrence of unacceptable immune related toxic side effects (immune myocarditis, pneumonia, etc.).
• Patients who were assessed as hyperprogressive disease (HPD).
• Patients who have received pelvic and abdominal radiation therapy within 6 months prior to enrollment.
• The adverse reactions from prior treatment have not yet recovered to a CTCAE5.0 rating of ≤ 1 (excluding toxicity that has been determined to be risk-free, such as fatigue or hair loss).
• Patients with active uncontrolled systemic bacterial, viral, or fungal infections despite optimal treatment.
• Significant liver or kidney dysfunction (i.e., laboratory values >3 times the upper limit of normal).
• Active hepatitis B, hepatitis C, HIV, or syphilis.
• Brain disorders, symptomatic central nervous system (CNS) or meningeal metastases, or impaired cognitive function.
• Hypersensitivity to any drug included in the trial.
• Drug and/or alcohol abuse.
• Pregnant or breastfeeding women.
• Concurrent participation in another therapeutic clinical trial.
• Poorly controlled pleural effusion, pericardial effusion, or ascites requiring frequent drainage (recurrence within ≤14 days after intervention).
• Major surgery within 30 days.
• Use of antibiotics, antifungals, antivirals, antiparasitics, or probiotics within 4 weeks before enrollment.