The role of replanning in fractionated intensity modulated radiotherapy for nasopharyngeal carcinoma

Abstract

Background and purpose Anatomic changing frequently occurred during fractionated radiotherapy. The aims of this study were to model the potential benefit of adaptive IMRT replanning during fractionated radiotherapy and its potential advantage over clinical outcome in patients with nasopharyngeal carcinoma. Materials and methods Thirty-three patients with repeat CT imaging and replanning were retrospectively analyzed. 66 case-matched control patients without replanning were identified by matching for AJCC stage, gender, and age. Hybrid IMRT plans were generated to evaluate the dosimetric changing. Mann–Whitney–Wilcoxon tests were used to evaluate the effect of replanning on volumetric and dosimetric outcomes within individuals. Kaplan–Meier estimators were used to estimate the survival function of patients with or without replanning. Results The mean volume of the ipsilateral and contralateral parotid glands decreased during the treatment. The hybrid IMRT plans showed decreased doses to target volumes and increased doses to normal structures in replanning. The clinical outcome comparison indicated that the IMRT replanning improved the 3 years local progression–free survival for patients who had AJCC staged more than T 3 (T 3,4N x ) and ease the late effects for patients who had large lymph nodes (AJCC stage T x N 2,3). Conclusion Repeat CT imaging and IMRT replanning were recommendatory for specific nasopharyngeal carcinoma patients.