Effect of CTV dose optimization in upper and middle neck on protecting the main midline structures in intensity-modulated radiotherapy for nasopharyngeal carcinoma / 中华放射肿瘤学杂志

ABSTRACT

Objective:To explore the significance of the clinical target volume (CTV) dose optimization in the upper and middle neck in protecting the laryngopharynx, anterior and posterior rings during intensity-modulated radiotherapy (IMRT) and multimodal imaging system for nasopharyngeal carcinoma.Methods:Clinical data of 298 nasopharyngeal carcinoma patients admitted to Jiangsu Cancer Hospital from 2016 to 2018 were retrospectively analyzed. According to the following five strategies of CTV dose optimization in the upper and middle neck group A, complete optimization of bilateral cervical lymph nodes (CLNs), that is, the CTV doses of bilateral CLNs were 50.4 Gy; group B, complete optimization of unilateral CLNs, that is, the CTV dose of unilateral CLNs was 50.4 Gy and the contralateral CLNs was 60 Gy; group C, incomplete optimization of bilateral CLNs, that is, the CTV doses of bilateral CLNs were 50.4 Gy, while the suspicious positive CLNs were selectively boosted to 60 Gy; group D, incomplete optimization of unilateral CLNs, that is, the CTV dose of unilateral CLNs was 50.4 Gy and the suspicious positive CLNs were selectively boosted to 60 Gy, and the CTV dose of contralateral side was 60 Gy; group E no optimization, that is, the CTV doses of bilateral CLNs were 60 Gy.Results:Among 298 patients, 215 patients received dose optimization and 83 cases did not receive dose optimization. In the dose optimization schemes, 114 cases were assigned in group A, 36 cases in group B, 60 cases in group C and 5 cases in group D. The median (range) follow-up time was 28.5(6.0-46.3) months. The overall survival rate was 95.6%, the progression-free survival rate was 84.2% and the locoregional control rate of CLNs was 98.0%. Local relapse of CLNs occurred in six patients, including 1 case of retropharyngeal lymph node, 4 cases of Ⅱ area and 1 case of Ⅳ area. The P values of average dose of laryngopharynx in group A, group B, group C and group D compared with that in group E were<0.001, 0.016, 0.001 and 0.572, respectively. The P values of the average dose of the anterior ring in group A, group B, group C and group D compared with that in group E were<0.001, 0.011, <0.001 and 0.805, respectively. The P values of the average dose of the posterior ring in group A, group B, group C and group D compared with that in group E were<0.001, 0.004, <0.001 and 0.252, respectively.Conclusions:Combined with the metastatic rules of CLNs and multimodal imaging system, it is safe to optimize the CTV dose of the upper and middle neck during IMRT in nasopharyngeal carcinoma patients, which can significantly reduce the doses of laryngopharynx, anterior and posterior rings, thereby providing evidence for reducing the CTV dose in the upper and middle neck.