Fruquintinib-Associated Posterior Reversible Encephalopathy Syndrome Complicated by Respiratory Failure: A Case Report

Background Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic disorder characterized by neurological symptoms and predominantly vasogenic edema on neuroimaging. PRES has been associated with vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors, but fruquintinib-associated PRES is rare, with only four cases previously reported. Case Presentation A 59-year-old woman with metastatic ascending colon cancer received fourth-line fruquintinib (5 mg/day; 3 weeks on, 1 week off). Her blood pressure was 168/97 mmHg on day 18 of the first cycle. After completing 21 days of treatment, she entered the scheduled off-treatment period. On day 23, she developed blurred vision, followed by generalized seizures and impaired consciousness on day 24. Brain magnetic resonance imaging (MRI) showed predominantly parieto-occipital cortical and subcortical lesions consistent with PRES. Fruquintinib was not resumed, and antiepileptic and antihypertensive treatment was initiated. Follow-up imaging showed marked improvement of the lesions. The Naranjo Adverse Drug Reaction Probability Scale score was 5, indicating a probable association between fruquintinib and PRES. However, progressive hypoxemia with pleural effusion subsequently developed, and the patient died from respiratory failure on day 32. Conclusion Fruquintinib-associated PRES should be considered in patients who develop neurological symptoms, particularly with new or worsening hypertension. Although respiratory failure progressed despite radiological improvement of PRES, a direct causal relationship between PRES and the fatal outcome could not be established. Early recognition and appropriate management of seizures and hypertension are important.