A nomogram to predict symptomatic epilepsy in patients with radiation-induced brain necrosis.

Abstract

To develop and validate a nomogram to predict epilepsy in patients with radiation-induced brain necrosis (RN). 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 (<i>C</i> index) and the calibration curve. The results were internally validated using bootstrap resampling and externally validated using 128 patients with RN from 2 additional hospitals. A total of 302 patients with RN with a median follow-up of 3.43 years (interquartile range 2.54-5.45) were included in the training cohort; 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, sex, and total cholesterol level. In the validation cohort, 28 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 <i>C</i> index 0.76 [training] vs 0.72 [95% confidence interval 0.62-0.81; validation]). Our study developed an easily applied nomogram for the prediction of RN-related epilepsy in a large RN cohort. This study provides Class III evidence that a nomogram predicts post-RN epilepsy.