a Study of QL1706 or QL1604 in Patients With Limited-stage Small Cell Lung Cancer After Chemoradiotherapy.

Inclusion Criteria: * The patient must be aged between 18 and 75 years (inclusive of boundary values), and both males and females are eligible. * Pathologically confirmed LS-SCLC \[I-III stage SCLC (any T, any N, M0)\], according to the American Joint Committee on Cancer (AJCC, 8th edition) staging manual. * Received 4 cycles of chemotherapy concurrent or sequential with radiotherapy. Chemotherapy must contain platinum and etoposide. Radiotherapy must be either total 60-70 Gy over 6 weeks for the QD regimen or total 45 Gy over 3 weeks for BID schedules. * Patients must have achieved a complete response (CR), partial response (PR), or stable disease (SD) after receiving curative platinum-based CRT and must not have developed progressive disease (PD) prior to study entry. Exclusion Criteria: * Mixed SCLC and non-small cell lung cancer (NSCLC). * Extensive-stage SCLC. * Active or prior documented autoimmune or inflammatory disorders. * Received other chemotherapy regimens besides etoposide and platinum-based therapy. * Active or prior documented autoimmune or inflammatory disorders. * Presence of interstitial lung disease or active non-infectious pneumonia (excluding grade 1 radiation pneumonitis not treated with corticosteroids).