Rapid effect of osimertinib re-challenge on brain metastases developing during salvage cytotoxic chemotherapy after osimertinib treatment failure: A case report.

We herein report a case of symptomatic brain metastases (BM) from lung adenocarcinoma in a 73-year-old female patient, which developed during salvage cytotoxic chemotherapy following failure of osimertinib treatment. The patient was proven to have a T790M mutation prior to osimertinib therapy, and achieved a clinical benefit from osimertinib for 3 years until the primary tumor progressed. Although active BM were not detected prior to initiating salvage cytotoxic chemotherapy, the patient developed numbness of the left hand, severe dizziness, and disturbance of behavior and thought after the 3-month course of the salvage cytotoxic chemotherapy. Brain magnetic resonance imaging revealed multiple BM with severe peritumoral brain edema. To avoid radiation-induced cognitive impairment, osimertinib re-challenge was undertaken. At 2 weeks after osimertinib initiation, the patient's neurological symptoms drastically improved. One month later, radiological evaluation revealed apparent shrinkage of the BM and subsiding brain edema, although the primary lung tumor remained stable. Therefore, osimertinib re-challenge may be a viable treatment option for BM developing during salvage cytotoxic chemotherapy.