Radiobiological modeling of acute esophagitis following radiotherapy of thorax and head-neck tumors: A comparison of Lyman Kutcher Burman with equivalent uniform dose-based models

Purpose: The current study aimed to compare performance of radiobiological models in predicting acute esophagitis (AE) complication after three-dimensional conformal radiation therapy (3D-CRT) with and without chemotherapy of thoracic, head and neck patients. Materials and methods: A total of 100 patients, 50 patients receiving with and 50 patients without concurrent chemotherapy were treated on the basis of five days a week for 3 months with different total doses and a daily dose range between 1.8 -2.4 Gy. Predictions of AE were based on Lyman–Kutcher–Burman (LKB) and Equivalent Uniform Dose (EUD)-based radiobiological models and 3 months of follow up were performed to monitor the complication incidence among the studied patients. ROC and univariable logistic regression analyses were performed and the effect of mean dose, volume percentage and weight loss percentage on the probability of AE grade  2 were studied.Results: EUD-based model showed better concordance with the clinical data for all patients (AUC=0.919) and the concurrent chemo-radiotherapy (CCRT) group (AUC=0.986). For radiation therapy group the LKB model had better performance than EUD-based model (AUC=0.921). The incidence of grade 2 esophagitis for chemoradiation and radiation therapy groups was observed 37.94 ± 4.0 and 68.39 ± 7.1 days after initiation of radiation therapy. Conclusions: The EUD-based model showed higher agreement with follow up data. The incidence time of grade  2 AE for CCRT was approximately two times shorter than non- CCRT group.