To evaluate the efficacy and safety of envafolimab combined with concurrent chemoradiotherapy in limited stage small cell lung cancer.

Envafolimab is the world's first subcutaneous injection of PD-L1 monoclonal antibody. Suitable for adult patients with advanced solid tumors with unresectable or metastatic microsatellite highly unstable (MSI-H) or mismatch repair gene defects (dMMR).

Inclusion Criteria:

• The result of histopathological or cytological diagnosis is small cell lung cancer.
• Diagnosed as limited stage by imaging examination (lesion limited to half chest and one radiotherapy field, without malignant pleural or pericardial effusion); And at least one measurable lesion that meets the RECIST 1.1 standard.
• Have not received systematic treatment in the past, and initially underwent 2 cycles of etoposide+cisplatin/carboplatin induction therapy.
• Age 18-75 years old, male or non pregnant female.
• The expected survival period is>3 months.
• ECOG score 0-1.
• Weight>30 kilograms.
• All patients underwent chest CT, head MRI, abdominal CT or MRI, and whole body bone scan before treatment to clarify.
• Hematological indicators: white blood cell (WBC) count ≥ 4 * 109/L, absolute neutrophil count (ANC) ≥ 1.5 * 109/L, hemoglobin (Hb) level>100 g/L, platelet (Plt) count>100 * 109/L, serum creatinine (Cr) level<1.5 times the upper limit of normal value, serum alanine transaminase (AST) and glutamic transaminase (ALT) levels<2.5 times the upper limit of normal value, and serum bilirubin level ≤ 1.5 times the upper limit of normal value.
• The patient has signed an informed notice and is willing and able to comply with the visit, treatment plan, laboratory examination, and other research procedures of the research plan.

Exclusion Criteria:

• Patients with non-small cell lung cancer or mixed components of small cell lung cancer in histopathology.
• Patients with extensive stage small cell lung cancer (ES-SCLC).
• Merge malignant pleural effusion and pericardial effusion.
• Pregnant and lactating women.
• Merge patients with more severe underlying diseases.
• Patients who have previously been treated with inhibitors of immune regulatory points (CTLA-4, PD-1, PD-L1, etc.).
• Patients may require long-term use of immunosuppressive drugs or systemic or local use of corticosteroids with immunosuppressive doses for comorbidities.
• Patients with immunodeficiency disorders and a history of organ transplantation (including but not limited to: interstitial pneumonia, uveitis, enteritis, hepatitis, pituitary inflammation, nephritis, hyperthyroidism, hypothyroidism; vitiligo or childhood asthma. Patients who have completely relieved and do not require any intervention after adulthood can be included; asthma that requires medical intervention with bronchodilators cannot be included).
• Those whose laboratory test values during the screening period before enrollment do not meet relevant standards.
• Patients with significantly reduced heart, liver, lung, kidney, and bone marrow function.
• Serious and uncontrolled internal diseases and infections.
• Simultaneously using other investigational drugs or in other clinical trials.
• Refusal or inability to sign informed consent form for participation in the experiment.
• A history of allergies to etoposide, cisplatin, or any excipients.
• Researchers have determined that patients are not suitable to participate in the study and are unlikely to comply with the study procedures, limitations, and requirements.