Unexpected late radiation neurotoxicity following bevacizumab use: a case series.

The purpose of this case series is to report the unexpected occurrence of four cases of late radiation-induced neurotoxicity with bevacizumab use following radiotherapy to the CNS. We retrospectively reviewed the case records of four patients, three with glioblastoma and one with bone metastases secondary to metastatic breast cancer, who were treated with radiotherapy and developed late radiation-induced neurotoxicity following bevacizumab use. Three cases of optic neuropathy in glioblastoma patients and a single case of Brown-Séquard syndrome in the thoracic spine of a patient with metastatic breast cancer are reported. We hypothesize that bevacizumab use following radiotherapy to the CNS may inhibit vascular endothelial growth factor-dependent repair of normal neural tissue, and thus may increase the risk of late radiation neurotoxicity. Phase III data on the safety and efficacy of bevacizumab use with radiation in the setting of glioblastoma is awaited.