Early‐Onset Posterior Reversible Encephalopathy Syndrome at Reduced‐Dose Sunitinib in Metastatic Papillary Renal Cell Carcinoma: A Case Report

Posterior reversible encephalopathy syndrome (PRES) is a rare but potentially life-threatening neurological complication associated with vascular endothelial growth factor (VEGF)-targeted tyrosine kinase inhibitors. Although it is typically reported after prolonged exposure and at standard or high doses, early onset at reduced dosing may occur and requires prompt recognition. We report a 64-year-old woman with metastatic papillary renal cell carcinoma who developed PRES after two months of treatment with reduced-dose sunitinib (37.5 mg daily). She presented with severe headache, nausea, vomiting, impaired consciousness, and reduced mobility, accompanied by acute hypertension (170/100 mmHg). Brain magnetic resonance imaging demonstrated bilateral vasogenic edema without diffusion restriction, consistent with PRES, and electroencephalography revealed generalized background slowing indicative of encephalopathy. Sunitinib was immediately discontinued, and the patient was treated with corticosteroids, antiepileptic therapy, and antihypertensive agents, resulting in rapid clinical improvement. Follow-up imaging confirmed complete radiological resolution. Subsequent treatment with nivolumab and axitinib achieved limited disease control, and the overall survival was 11 months. This case highlights that PRES can develop early and at reduced doses of sunitinib, may present with severe neurological impairment, and can be supported by electroencephalographic findings. Early recognition and prompt discontinuation of the offending agent are essential to prevent irreversible neurological damage.