ABSTRACT
Background: Radiotherapy is considered a compromise between the amount of killed tumor cells and the damage caused to the healthy tissue. Regarding this, radiobiological modeling is performed to individualize and optimize treatment strategies. Objective: This study aimed to determine the normal tissue complication probability (NTCP) of acute ocular pain following radiotherapy. Material and Methods: In this prospective observational study, the clinical data were collected from 45 patients with head and neck cancers and skull-base tumors, and dosimetric data were recorded after contouring the eye globe. Acute ocular pain was prospectively assessed with a three-month follow-up. The Lyman-Kutcher-Berman (LKB) parameters were estimated using the Area Under Curve (AUC) of Receiver Operating Characteristic (ROC) maximization and Maximum Likelihood (MLH) methods, and the NTCP of acute ocular pain was then determined using generalized LKB radiobiological model. The model performance was evaluated with AUC, Brier score, and Hosmer-Lemeshow tests. Results: Six out of 45 (13.33%) patients developed acute ocular pain (grade 1 or more). LKB model showed a weak dose-volume effect (n=0.09), tolerance dose for a 50% complication (TD50) of 27.54 Gy, and slope parameter (m) of 0.38. The LKB model showed high prediction performance. The LKB model predicted that NTCP would be less than 25% if the generalized equivalent uniform dose (gEUD) was kept below 20 Gy. Conclusion: The LKB model showed a high performance in determining the NTCP of ocular pain so that the probability of ocular pain will be less than 25% if the eye globe mean dose is kept below 12 Gy.
ABSTRACT
PURPOSE: Radiation therapy is broadly used as one of the main treatment methods for patients with head and neck cancers and skull base tumors. However, it can lead to normal tissue complications. Therefore, this study aimed to model normal tissue complication probability (NTCP) of eyelid skin erythema after radiation therapy. METHODS: The dataset of 45 patients with head and neck and skull base tumors was prospectively collected from their dose-volume histograms (DVHs). Grade 1 + eyelid skin erythema based on the Common Terminology Criteria for Adverse Events (CTCAE 4.0) was evaluated as the endpoint after a three-month follow-up. The Lyman-Kutcher-Burman (LKB) radiobiological model was developed based on generalized equivalent uniform dose (gEUD). Model parameters were calculated by maximum likelihood estimation. Model performance was evaluated by ROC-AUC, Brier score and Hosmer-Lemeshow test. RESULTS: After three months of follow-up, 13.33% of patients experienced eyelids skin erythema grade 1 or more. The parameters of the LKB model were: TD50 = 30 Gy, m = 0.14, and n = 0.10. The model showed good predictive performance with ROC-AUC = 0.80 (CI:0.66-0.94) and a Brier score of 0.20. CONCLUSIONS: In this study, NTCP of eyelid skin erythema was modeled based on the LKB radiobiological model with good predictive performance.
