Complete Remission of Multiple Brain Metastases in a Patient with -Mutated Non-Small-Cell Lung Cancer Treated with First-Line Osimertinib without Radiotherapy.

Osimertinib has demonstrated efficacy against stable or asymptomatic central nervous system (CNS) metastases of epidermal growth factor receptor () mutation-positive non-small-cell lung cancer (NSCLC) in phase 2 and 3 clinical trials that allowed prior CNS radiotherapy. However, the efficacy of osimertinib only or the optimal treatment combination or sequence of radiotherapy has not been investigated. A 74-year-old woman diagnosed with T4N1M1c Stage IVB lung adenocarcinoma with mutation presented with a left upper lobe mass and multiple bilateral lung metastases. A total of more than 20 asymptomatic multiple brain metastases with a maximum diameter of 12 mm were diagnosed simultaneously. Osimertinib was administered as first-line treatment. Whole brain radiotherapy was deferred because she had no neurological symptoms. After 5 weeks, the multiple brain metastases disappeared completely, together with the response in the lung lesions. This case demonstrated that first-line treatment with osimertinib could even achieve complete remission of multiple brain metastases comprising as many as twenty lesions of -mutated NSCLC without radiation therapy. Radiation therapy for brain metastases can be deferred or even withheld. A new treatment strategy for mutated NSCLC with CNS metastases should be investigated using osimertinib, especially regarding optimal combination or sequence of radiotherapy.