Brain Atrophy and Leukoencephalopathy Following Tarlatamab: Case Report.

We describe the case of a 74-year-old female diagnosed with extensive-stage small cell lung cancer. Initially, she received carboplatin, etoposide and atezolizumab, followed by amrubicin as second-line treatment and nogitecan as third-line treatment. Stereotactic radiotherapy was delivered to subsequent brain metastases. Two years after the initial treatment, new brain and lung metastases developed. Whole-brain radiotherapy was administered, followed by tarlatamab (1 mg on Day 1, 10 mg on Days 8 and 20). After the third dose of tarlatamab, the patient developed disorientation. Brain magnetic resonance imaging revealed shrinkage of the metastatic lesions, rapid cerebral atrophy, ventricular enlargement and periventricular hyperintensity on fluid-attenuated inversion recovery imaging. Dexamethasone was initiated without neurological improvement. The early-onset cerebral atrophy and leukoencephalopathy in the current case was attributed to whole brain radiotherapy and tarlatamab. Patients with brain metastases may be at increased risk of neurological events associated with tarlatamab.