Extensive Stage Small-Cell Lung Cancer with Cystic Brain Metastases: A Report of Two Cases.

Objective: Cystic brain metastases (BMs) are rare in small cell lung cancer (SCLC), and there are limited data on the treatment and prognosis of cystic BMs. Whole brain radiotherapy has been the mainstay for BMs since several years. Immune checkpoint inhibitors in extensive stage small cell lung cancer (ES-SCLC) have been shown to be suitable for patients who experienced better overall survival and progress-free survival and have been approved as the first-line treatment for ES-SCLC. In this report, we described two ES-SCLC patients developed cystic BMs after immunotherapy, after which the patients continued to treat the primary lesion with immune checkpoint inhibitors and the cystic BMs with radiotherapy. Case Description: Two male patients were diagnosed with ES-SCLC at the first admission and were subsequently treated with immunotherapy plus platinum therapy, during which cystic BMs developed. One patient received whole brain radiotherapy and the other received whole brain radiotherapy and Gamma knife radiosurgery (GKRS). Immunotherapy was continued after the brain lesions were controlled. It has been 33 months since the first patient was diagnosed and is now in stable condition. The other patient achieved an overall survival of 30 months. Conclusion: This report describes two patients with cystic brain metastases in ES-SCLC. Whole brain radiotherapy has a good effect on local control of cystic brain metastases in small cell lung cancer and can significantly improve the symptoms of patients. At the same time, we treat immunotherapy as the first-line treatment, and then perform cross-immunotherapy after disease progression, combined with anti-vascular targeting drugs. The patient did not develop severe iRAEs.