Intracranial antitumor efficacy of combination treatment with encorafenib plus binimetinib in BRAF V600E-mutated anaplastic thyroid carcinoma.

The intracranial antitumor efficacy of combination therapy with BRAF and MEK inhibitors in BRAF-mutated thyroid cancer has not been reported. Here, we describe a case of anaplastic thyroid cancer harboring BRAF V600E mutation with brain metastases which was treated with encorafenib plus binimetinib. The patient was initially diagnosed with T4bN1bM1 and experienced disease progression following surgery and lenvatinib treatment. Encorafenib plus binimetinib was initiated as second-line treatment seven months after the surgery. After achieving sustained disease stabilization, a solitary asymptomatic brain metastasis was detected following a three-week interruption due to COVID-19 infection. The lesion shrank after only two weeks of resumed encorafenib plus binimetinib, and additional stereotactic radiosurgery was performed without significant adverse events. This case suggests that the combination of BRAF and MEK inhibitors may be a viable treatment option for brain metastasis in BRAF-mutated thyroid cancer, despite general prioritization of local treatments. In addition, encorafenib plus binimetinib treatment may suppress the growth of microscopic metastasis. This possibility is supported by reliable evidence for the use of BRAF plus MEK inhibitor for brain metastasis from BRAF-mutated malignant melanoma. We conclude that encorafenib plus binimetinib treatment for brain metastasis from BRAF-mutated thyroid cancer is a safe and effective treatment choice.