Tislelizumab Plus Lenvatinib in Stage III-IV RCC

Inclusion Criteria: * Willing and able to provide written informed consent * Age ≥ 18 years * Subjects with pathologically and radiologically confirmed renal cell carcinoma: Stage III/IV * There are no suspected brain metastases * There are lesions that can be measured by imaging * Eastern Cooperative Oncology Group (ECOG) Performance Status of 0-1 * Organ function level must meet the following requirements: Hematological indexes: neutrophil count \>= 1.5x10\^9/L, platelet count \>= 100x10\^9/L, hemoglobin \>= 9.0 g/dl (can be maintained by blood transfusion); Liver function: total bilirubin \<=1.5 ULN, alanine aminotransferase and aspartate aminotransferase \<=1.5 ULN * Women were required to use an effective contraceptive method for three months after the end of the study, and men were required to consent to use an effective contraceptive method with their spouse during and for three months after the end of the study * The subjects volunteered to join the study, signed informed consent, and had good compliance with follow-up Exclusion Criteria: * Prior treatment with radiation, chemotherapy, long-term or high-dose hormone therapy, or immune checkpoint inhibitors * Previous or concurrent other malignancy * Previous PD-L1 or PD-L1 treatment, or allergy to PD-L1 * History of primary immunodeficiency * Active, known or suspected autoimmune diseases * Known history of allogeneic organ transplantation and allogeneic hematopoietic stem cell transplantation * Pregnant or lactating female patients; * Untreated acute or chronic active hepatitis B or hepatitis C infection. Under the condition of monitoring the virus copy number of patients receiving antiviral treatment, doctors can judge whether they are in line with the patients' individual conditions; * Have a clear history of active tuberculosis; * Participating in other clinical researchers; * Men with reproductive capacity or women who are likely to become pregnant do not take reliable contraceptive measures; * Uncontrolled concurrent diseases, including but not limited to: HIV infected (HIV antibody positive); Severe infection in active stage or poorly controlled; Evidence of serious or uncontrollable systemic diseases (such as severe mental, neurological, epilepsy or dementia, unstable or uncompensated respiratory, cardiovascular, liver or kidney diseases, uncontrolled hypertension \[i.e. hypertension greater than or equal to CTCAE grade 2 after drug treatment\]); Patients with active bleeding or new thrombotic disease