Background: Small-cell lung cancer (SCLC) is highly malignant. Despite being highly sensitive to initial chemotherapy and radiotherapy, the recurrence rate is high. Atezolizumab is the first immune checkpoint inhibitor (ICI) that has been proven to provide an overall survival (OS) benefit for extensive-stage SCLC (ES-SCLC), making ICIs in combination with chemotherapy the standard first-line treatment for ESSCLC. However, the real-world treatment of SCLC is more complex, and multimodal therapy may be needed to achieve long-term patient survival. Few reports on later-line chemotherapy combined with immunotherapy have been published thus far. Moreover, there is limited data on the efficacy and safety of thoracic radiotherapy and radiotherapy for metastatic lesions after multiple lines of treatment have failed in ES-SCLC, and the value of small-molecule antiangiogenesis combined with immunotherapy also needs further exploration. Case Description: A patient was diagnosed with mediastinal limited-stage SCLC (LS-SCLC) and experienced local progression following standard chemoradiotherapy and prophylactic cranial irradiation. Subsequently, the patient underwent second-line irinotecan chemotherapy, which resulted in severe hematological toxicity. Upon initiation of third-line therapy with anlotinib, the disease remained stable for 9 months. Unfortunately, imaging revealed the presence of a new lesion at the right lung apex. Nevertheless, there was renewed hope for survival when atezolizumab was introduced as part of the treatment regimen. Despite the later development of brain metastases and metastasis adjacent to the aortic arch, long-term survival was achieved through combination therapy involving immunotherapy, antiangiogenic therapy, and radiotherapy targeting the metastatic lesions. By March 2024, the OS had reached 70 months, with a duration of treatment with atezolizumab of 48 months, and only grade II hypothyroidism occurred during treatment, with no other immunotherapy-related adverse events being observed. Conclusions: This case report suggests the potential efficacy and safety of integrating chemotherapy, immunotherapy, radiotherapy, and antiangiogenic therapy for the treatment of SCLC. Further clinical trials are warranted to validate the value of combining chemotherapy, immunotherapy, radiotherapy, and antiangiogenic therapy.