A Nomogram to Predict Symptomatic Epilepsy in Patients with Radiation-induced Brain Necrosis.

Objective: This study aimed to develop and validate a nomogram to predict epilepsy in patients with radiation-induced brain necrosis (RN). Methods: The nomogram was based on a retrospective analysis of 302 patients who were diagnosed with symptomatic RN from January 2005 to January 2016 in Sun Yat-sen Memorial Hospital using the Cox proportional hazards model. Discrimination of the nomogram was assessed by the concordance index (C-index) and the calibration curve. The results were internally validated using bootstrap resampling and externally validated using 128 RN patients from two additional hospitals. Results: A total of 302 RN patients with a median follow-up of 3.43 years (IQR 2.54-5.45) were included in the training cohort, among which 65 (21.5%) developed symptomatic epilepsy during follow-up. Seven variables remained significant predictors of epilepsy after multivariable analyses: MRI lesion volume, creatine phosphokinase, the maximum radiation dose to the temporal lobe, RN treatment, history of hypertension and/or diabetes, gender, and total cholesterol level. In the validation cohort, twenty-eight out of 128 (21.9%) patients had epilepsy after RN within a median follow-up of 3.2 years. The nomogram showed comparable discrimination between the training and validation cohort (corrected C-index 0.76 [training] vs. 0.72 [95% CI 0.62-0.81; validation]). Conclusion: Our study developed an easily applied nomogram for the prediction of RN-related epilepsy in a large RN cohort. Classification of Evidence: This study provides Class III evidence that a nomogram predicts post-RN epilepsy.