NTCP Modeling of Visual Processing Speed Impairment and Related Factors Following Radiotherapy in Patients with Brain Metastases

Abstract

Background:There have been numerous reports of impairment in neurocognitive functions, including visual processing speed (VPS), among patients who have developed brain metastasis. Therefore, this study aims to develop a model that calculates the probability of normal tissue complication arising from VPS impairment after whole-brain radiotherapy.Materials and Methods:In this study, 18 patients were examined for VPS impairment at the 4-month follow-up. After the hippocampus delineation, dose-volume histograms (DVHs) were generated. Normal tissue complication probability (NTCP) models were calculated for VPS using the Lyman model and multivariable logistic regression analysis.Results:VPS was observed in 33.3 of patients. TD50 was obtained at 38.43 Gy. The most predictive variable in univariate analysis was V-Tot, but none of the dosimetric and clinical variables were selected as predictive variables in the multivariate regression analysis (P > 0.05). The overall predictive performance of both models was satisfactory; however, multivariate logistic regression was superior.Conclusion:This study modeled the probability of VPS following irradiation of the hippocampus. The NTCP curve showed that by keeping a maximum dose of hippocampi less than 20 Gy, NTCP becomes <25.