Complete and long-lasting response to immunotherapy in a stage IV non-small cell lung cancer with brain metastasis.

Approximately 20% of lung cancer patients have brain metastasis at diagnosis, which is associated with a worse prognosis and a negative impact on quality of life. The emergence of new systemic treatment options such as immune checkpoint inhibitors (ICI) and targeted therapies changed the prognosis for stage IV lung cancer patients. However, the impact of local and systemic treatment sequencing in patients with stage IV lung cancer and brain metastasis is still unclear. We present the case of a 51-year-old man with stage IV non-small cell lung cancer and brain metastasis at diagnosis who underwent whole brain radiotherapy (WBRT) and achieved intracranial and extracranial complete response after second-line treatment with an ICI. Currently, the patient has an overall survival of 87 months and a progression-free survival of 73 months with an optimal quality of life. We hypothesized that treatment sequencing of WBRT and immunotherapy could explain this unexpected outcome.