Safety and Tolerability of LDRT Plus Concurrent Partial SBRT and Tislelizumab in Patients With Bulky Tumors

Inclusion Criteria: 1. Be willing and able to provide written informed consent/assent for the trial. 2. Be ≥18 years of age on day of signing informed consent. 3. Patients with histologically or cytologically confirmed stage IV solid tumours. 4. Be willing to undergo repeat biopsy of tumor lesions according to the study protocol. 5. Patients who have failed the standard therapy, or who are unsuitable for standard treatment, or refuse chemotherapy. 6. At least one measurable lesion according to RECIST 1.1. A lesion that has previously received radiotherapy can be considered a target lesion only if this lesion is clearly progressed after radiotherapy. 7. The target lesions (irradiated lesions) are \> 5cm in in diameter 8. ECOG 0-2. 9. Life expectancy of \> 3 months. 10. Subjects should agree to use an adequate method of contraception. Exclusion Criteria: 1. Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis and/or spinal cord compression, etc. 2. With oncologic emergencies that require immediate treatment 3. EGFR/ALK/ROS-1 mutation or mutation status unknown. 4. Has evidence of interstitial lung disease or active and/or non-infectious pneumonitis (drug-induced pneumonia, radiation-induced pneumonia, etc.) requiring steroid therapy. 5. History of pulmonary fibrosis, pulmonary hypertension, severe irreversible airway obstruction disease 6. Patients with peripheral neuropathy. 7. Significant heart disease or impairment of cardiac function 8. Fluid accumulating in the third space, such as pericardial effusion, pleural effusion and peritoneal effusion that remains uncontrolled by aspiration or other treatment 9. Known allergy to drugs or excipients, known severe allergic reaction to any of the PD-1 monoclonal antibodies 10. Known allogeneic organ transplantation (except corneal transplantation) or allogeneic hematopoietic stem cell transplantation.