Abstract
Three years ago, a 74–year–old man underwent a surgery for stage IA lung adenocarcinoma with a mutation of epidermal growth factor receptor (EGFR) and had no recurrence ever since. Two months ago, he started experiencing headaches, photophobia, and a progressive deterioration in activities of daily living (ADL). He also experienced a rapid disturbance of consciousness while seeing his former doctor. Afterward, he was admitted to our hospital. The head MRI revealed enhancement of the meninges. Atypical cells derived from adenocarcinoma were detected in the cerebrospinal fluid cytology, and the patient was diagnosed with leptomeningeal metastasis. After an emergency lumbar drainage procedure, a therapy with osimertinib, a third–generation EGFR tyrosine kinase inhibitor (EGFR–TKI), was initiated. Leptomeningeal metastasis is one of poor prognostic factors and usually occurs in advanced stages of cancer. Nevertheless, osimertinib was able to successfully eradicate metastatic lesions in this patient. Therefore, this third–generation EGFR–TKI may constitute an effective first–line treatment for severe leptomeningeal metastasis associated with EGFR mutation–positive lung cancer. And even if the state of primary tumor detected at an early stage and metastasis has not been confirmed before, it must be remarked that the possibility of the onset of leptomeningeal metastasis still remains.
