Omitting CTV for Primary Tumor in LS-SCLC

Inclusion Criteria: 1. Small cell lung cancer confirmed by histology or cytology; TNM stage IA-IIIC (AJCC 8th edition, 2017; limited-stage) without intrapulmonary metastasis; 2. Aged 18-75 years, KPS score ≥ 80, ≤ 10% weight loss within the past 6 months; 3. Have measurable lesions per RECIST 1.1 criteria; 4. Have no disease progression after 2-4 cycles of etoposide/carboplatin or etoposide/cisplatin; 5. Lung function test: FEV1 ≥ 1 L (Optional); 6. Complete blood count: neutrophil count ≥ 1.5 x 10\^9/L, hemoglobin ≥ 100 g/L, platelet count ≥ 100 x 10\^9/L; 7. Renal function: serum creatinine ≤ 1.5 x upper limit of normal (ULN); 8. Liver function: AST and ALT ≤ 2.5 x ULN, bilirubin ≤ 1.5 x ULN; 9. Fully understand the study, able to complete treatment and follow-up, and voluntarily sign the informed consent. Exclusion Criteria: 1. Other malignant tumors (prior or concurrent), except those that have been curatively treated with disease-free survival ≥ 5 years, such as non-melanoma skin cancer, cervical carcinoma in situ, or early-stage papillary thyroid cancer; 2. Uncontrolled heart disease or myocardial infarction within the past 6 months; 3. Patients with a history of mental illness; 4. Pregnant and lactating patients; 5. Poorly controlled diabetes and hypertension; 6. Interstitial pneumonia or active pulmonary fibrosis; 7. Active infection; 8. Other conditions unsuitable for enrollment (per investigator judgment).