For limited-stage small cell lung cancer (SCLC), surgical treatment is recommended for patients with T1-2N0M0 (I-IIA) by guidelines. However, whether perioperative immunotherapy extends radical surgery to stage IIB-IIIB patients with improved survival remains elusive.

This is a phase II, single-arm study to evaluate the efficacy and safety of neoadjuvant Tislelizumab + chemotherapy (Cisplatin/Carboplatin + Etoposide) followed by radical surgery and adjuvant Tislelizumab ± chemotherapy for patients with limited-stage SCLC.

Inclusion Criteria:

1. Able to provide written informed consent and understand and agree to comply with the study requirements and assessment schedule;

2. Aged 18-75 years at the time of signing the informed consent form;

3. Pathologically (histologically or cytologically) confirmed diagnosis of small cell lung cancer;

4. Limited-stage disease (stage IIB-IIIB according to AJCC 8th edition) assessed by bronchoscopy, PET-CT, endobronchial ultrasound (EBUS), mediastinoscopy, or percutaneous biopsy, deemed resectable with curative intent (R0 resection) by the investigator.

   TNM staging includes T3-4 (N0 only) or N1-2 (any T) and M0, where T4 is limited to tumors >7 cm in diameter; Patients with tumors invading the diaphragm, mediastinum, heart, great vessels, trachea, recurrent laryngeal nerve, esophagus, vertebral body, carina or having separate tumor nodules in different ipsilateral lobes are excluded. N2 is limited to single station and non-bulky.

5. No prior radiotherapy, chemotherapy, immunotherapy, surgery or other systemic treatments;

6. ECOG PS score of 0-1;

7. Expected survival must be >3 months;

8. Adequate bone marrow reserve and organ function within 30 days prior to enrollment meeting criteria for receiving platinum-based doublet chemotherapy;

9. No contraindications for immunotherapy.

Exclusion Criteria:

1. Tumor histopathology indicates non-small cell lung cancer (NSCLC);
2. Presence of clinically inactive or active brain metastases;
3. Any history of interstitial lung disease (ILD) (including pulmonary fibrosis or radiation pneumonitis), current ILD, or suspicion of such diseases based on imaging during screening;
4. Receiving systemic corticosteroid therapy within 14 days prior to the first dose of study drug;
5. Previous radiotherapy, chemotherapy, immunotherapy, surgery, or other systemic treatments;
6. Any active malignancy within 2 years prior to enrollment;
7. Women who are pregnant, breastfeeding, or planning to become pregnant during the study period;
8. Uncontrolled or significant cardiovascular disease at the time of enrollment;
9. Active or previously recorded autoimmune or inflammatory diseases before enrollment;
10. History of active primary immunodeficiency disorders;
11. Presence of active infections;
12. Active bleeding disorders within ≤6 months prior to administration of the study drug, including gastrointestinal bleeding evidenced by hematemesis, severe hemoptysis, or melena;
13. Non-healing wounds, active peptic ulcers, or fractures;
14. Any condition that the investigator deems makes the patient unsuitable for participation in the study.

The clinical data including patient characteristics, CT images and pathology images.