Inclusion Criteria:
1. Age: 18-80 years old, male or female
2. Patients with pathologically confirmed extensive stage small cell lung cancer (according to the Veterans Administration Lung Study Group, VALG staging)
3. Never received prior systemic therapy for extensive stage small cell lung cancer
4. Have a measurable tumour target lesion (meeting RECIST 1.1 criteria)
5. Expected survival \> 3 months
6. ECOG PS: 0-1 points
7. Normal function of major organs
8. Women of childbearing potential must undergo a negative pregnancy test (βHCG) prior to initiation of treatment, and women of childbearing potential and men (who are sexually active with women of childbearing potential) must agree to use effective contraception uninterruptedly for the duration of the treatment period and for 6 months after the administration of the last therapeutic dose
9. Patients voluntarily enrolled in this study by signing an informed consent form
Exclusion Criteria:
1. Previous or concurrent other malignant tumours within 5 years, except cured basal cell carcinoma of the skin, carcinoma in situ of the cervix, superficial or non-invasive bladder cancer
2. Active tuberculosis infection, or a history of previous tuberculosis infection
3. Uncontrolled, symptomatic brain metastases that are not effectively controlled or a history of psychiatric illness that cannot be easily controlled or severe intellectual or cognitive dysfunction
4. Subjects with active, known or suspected autoimmune disease, hypothyroidism requiring only hormone replacement therapy, skin disorders not requiring systemic therapy (e.g., vitiligo, psoriasis, or alopecia areata) may be eligible for enrolment
5. Uncontrollable pleural effusion, pericardial effusion or ascites requiring repeated drainage
6. Subjects with the presence of any severe and/or uncontrolled disease
7. Imaging showing tumour invasion of large vessels or poor demarcation from large vessels
8. Susceptibility to bleeding, risk of hemoptysis, and history of significant coagulation disorders
9. History of psychotropic substance abuse, alcoholism or drug addiction
10. Active hepatitis (Hepatitis B reference: HBsAg positive with HBV DNA test value exceeding the upper limit of normal value Hepatitis C reference HCV antibody positive with HCV viral titre test value exceeding the upper limit of normal value)
11. Human immunodeficiency virus (HIV, HIV 1/2 antibody) positive
12. Patients who are unable to comply with the trial protocol or who are unable to cooperate with follow-up visits
13. Patients who, in the opinion of the investigator, should not be enrolled in the trial
