Symptomatic radiation necrosis in brain metastasis patients treated with stereotactic radiosurgery and immunotherapy

Objectives: The association of symptomatic radiation necrosis (RN) with stereotactic radiosurgery (SRS) and immune checkpoint inhibitors (ICIs) in brain metastases patients has been incompletely explored. We aim to discuss the incidence, risk factors, and prognosis of symptomatic RN in patients treated with these modalities. Patients and methods: We retrospectively evaluated the incidence of symptomatic RN among all patients with brain metastases treated with both SRS and an ICI at a single academic center. Risk factors for the development of symptomatic RN were determined, along with median overall survival (OS) stratified by the development of RN. Results: Between 2010 and 2016, 57 brain metastases patients were treated with both SRS and an ICI. Only 4 (7%) developed symptomatic RN. Symptomatic RN lesions were more likely to be located in the cerebral cortex (p = 0.019) and be associated with a primary renal cell carcinoma (p = 0.032). Median OS was 32 months for those who developed symptomatic RN and 29 months for all other patients (p = 0.16). Conclusion: Treatment of brain metastases with both SRS and an ICI is an effective modality that poses mild risk for developing symptomatic RN when compared to the risk of RN from SRS alone.