Isolated Progression of Miliary Brain Metastasis in a Patient with Stable Lung Adenocarcinoma Successfully Treated with Whole-brain Radiotherapy: A Case Report

Miliary brain metastasis is a rare form of metastasis commonly associated with advanced stages of cancer. In this article, we report a case of a 38-year-old male with solitary progression of miliary brain metastasis originating from stage 4 EML-ALK-positive lung adenocarcinoma. Multiple brain lesions were first detected upon the patient's inclusion in a brigatinib clinical trial. The brain lesions dissipated, and the lung and bone lesions decreased in size after starting the brigatinib therapy; however, the brain lesions later increased in number. A biopsy revealed miliary brain metastasis of lung adenocarcinoma. The patient was successfully treated with whole brain therapy, in addition to brigatinib. This case suggests that it is possible for an isolated miliary brain metastasis to occur during the effective suppression of systemic cancer progression. Whole brain radiotherapy while continuing effective systemic therapy is a good strategy for such patients.