An Analysis of Risk Factors for Radiation Necrosis Following Cranial Radiation.

Introduction Radiation necrosis in the brain is a frequent complication of brain radiation therapy (RT) and is characterized by various neurological symptoms including cognitive dysfunction, headaches, weakness, apraxia, aphasia, and numbness. These symptoms may be progressive and treatment-resistant. Currently, risk factors for radiation necrosis are not well characterized. The goal of this study is to identify risk factors for cerebral radiation necrosis in order to improve clinicians' ability to appropriately weigh the risks and benefits of brain RT. Methods A retrospective chart review was performed on patients who were diagnosed with brain tumors and received RT (3D conformal therapy, volumetric modulated arc therapy, stereotactic radiosurgery, or stereotactic radiotherapy) at the University of Arkansas for Medical Sciences from July 1, 2017, to July 1, 2019. Data regarding demographics, characteristics of cancer, chemotherapy status and class, comorbidities, and additional medications of patients were collected via EPIC. Total RT dose, fraction size, volume of brain receiving 12 Gy (V12), and retreatment of locally recurrent tumors were recorded from Eclipse. The diagnosis of radiation necrosis was based on MRI reports that were examined for a time period of 24 months following the completion of radiation treatment and confirmed, when possible, by biopsy. Cases that did not have an MRI available at least two months after the completion of RT were excluded. Statistical association analyses were used to identify candidate risk factors to radiation necrosis. These candidate risk factors were further used to assess their associations to demographics and other characteristics of cancer and treatments. Finally, adjusted and unadjusted logistic regression models were used to predict radiation necrosis using a single risk factor or multiple risk factors. ROC curves were used to evaluate the performance of prediction or discrimination of the logistic regression models. Results A total of 139 patients were studied. The mean ± standard deviation (SD) for age was 60.4 ± 13.6 years, female:male ratio was 71:68, and White:African American:other race ratio was 112:24:3. A total of 43 (30.9%) patients were diagnosed with radiation necrosis. Radiation adjuvant to surgery, concurrent systemic therapy status, total dose, and V12 were found to be significantly associated with radiation necrosis and considered candidate risk factors of radiation necrosis in the study. Predictive models showed adjusted odds ratios ([aORs] 95% confidence intervals or CIs) of 3.70 (1.01-13.56) and 8.19 (1.78-37.78) with radiation adjuvant to surgery and concurrent systemic therapy, respectively. For every one unit (log-transformed) increase of total dose and V12, the aORs (95% CI's) were 27.35 (3.74-200.16) and 1.63 (1.15-2.32), respectively. Conclusion Our study suggested a positive correlation of concurrent systemic therapy status and post-surgical adjuvant RT with the incidence of radiation necrosis. It further demonstrated that greater total RT dose and V12 were related to the risk of developing radiation necrosis following brain RT. Given the findings of this study, the aforementioned factors should be considered when weighing the risk of radiation necrosis with the benefits of treatment.