Posterior Reversible Encephalopathy Syndrome after Lenvatinib Therapy in a Patient with Anaplastic Thyroid Carcinoma

Posterior reversible encephalopathy syndrome (PRES) is a rare reversible neurological syndrome that causes subcortical vasogenic brain edema and which is associated with the use of target-specific agents. Lenvatinib is a target-specific agent that was recently approved for inoperable thyroid cancer. We herein describe the case of a 66-year-old woman with anaplastic thyroid cancer (ATC) who was treated with lenvatinib and who subsequently developed PRES. The clinical and radiological findings improved after suspending therapy for 1 week, and there was no recurrence with intermittent lower-dose lenvatinib treatment. Lenvatinib may prolong survival in patients with ATC and can be administered intermittently, even after PRES onset.