YO26 - Exacerbation of radiation necrosis around the radiotherapy-pretreated brain metastases site after immune checkpoint inhibitors.

Case summary

As the survival of patients with brain metastases is being prolonged, due to improved systemic therapy, opportunities to use immune checkpoint inhibitor (ICI)s after SRT (stereotactic radiotherapy) or IMRT (Intensity Modulated Radiation Therapy) in patient with brain metastases are increasing. Radiation necrosis is known as a late toxicity of SRT and IMRT. However, few studies have examined the association between ICIs and radiation necrosis. Here we report two cases in which radiation necrosis was exacerbated after ICIs.

Case1: A 30-year-old female diagnosed with nasopharyngeal carcinoma who had direct invasion to the skull base and metastases to the vertebrae. After the concurrent chemoradiation, she had a locoregional recurrence. MRI showed the ring-enhancing lesion around the IMRT-pretreated site of the right temporal lobe, which was considered to be radiation necrosis. One week after the initiation of nivolumab, the patient developed disorientation and a headache. Brain CT showed the exacerbation of radiation necrosis. Corticosteroid administration improved the symptoms. Nivolumab was not reinitiated.

Case2: A 60-year-old male diagnosed with non-small cell lung cancer with brain metastases. He underwent IMRT for the right temporal lobe after undergoing bilateral craniotomy for multiple brain metastases. Because the paralysis progressed, he was performed resection of the brain enhancing lesion. The histopathological examination of the resected brain lesion revealed the presence of diffuse necrosis and gliosis with absence of viable tumor, which was compatible with radiation necrosis. One week after the initiation of atezolizumab, the patient developed hemiparesis. Brain CT showed the exacerbation of radiation necrosis. The patient then started treatment with corticosteroid, and hemiparesis was partly improved. The administration of atezolizumab was discontinued.

Conclusion: We experienced two cases of exacerbation of radiation necrosis following the initiation of the ICIs. Further investigation for the safety of using ICIs in patients with radiation necrosis is warranted.

Clinical trial identification

Editorial acknowledgement