EGFR and Thrombocytopenia: Erlotinib 150 mg/day was introduced based on reports of dose‐dependent CNS efficacy, resulting in prompt improvement of neurological symptoms; however, grade 3 thrombocytopenia led to treatment interruption, followed by rapid neurological decline and death. This case illustrates that reduced‐dose EGFR TKI therapy, even with a CNS‐penetrant agent such as osimertinib, may provide insufficient cerebrospinal fluid drug exposure to prevent CNS progression.