Organoid-guided vs Topotecan Therapy in Relapsed Extensive-Stage Small Cell Lung Cancer

This study aims to provide personalized treatment options for patients with extensive-stage small cell lung cancer (SCLC) whose disease has worsened after initial chemotherapy. Researchers will use a novel approach called "tumor organoid drug sensitivity testing": A small sample of the patient's tumor (from biopsy or fluid) is grown into miniature 3D tumor models ("organoids") in the lab. These organoids are exposed to various FDA-approved second-line drugs (including chemotherapy and newer targeted/immunotherapy drugs if available). The most effective drug for each patient's organoids will be recommended for their treatment. 128 participants will be randomly assigned to one of two groups:Experimental Group: Receive organoid-guided personalized therapy; Control Group: Receive standard second-line chemotherapy (Topotecan). The study will compare: How long the cancer remains controlled (Progression-Free Survival); Overall survival time; Treatment response rates and side effects. Potential benefits: May identify more effective treatments for individual patients; Could extend time without cancer progression. Risks: Organoid testing requires an additional tumor biopsy/fluid collection; Possible side effects from second-line drugs.