Abstract:

Objective To assess the effect of optimizing the neck node level Ⅳ in IMRT clinical target volume（CTV）for nasopharyngeal carcinoma（NPC）on the treatment outcome and thyroid dose， in order to provide the basis for optimization of IMRT target area in NPC. Methods For selected 64 cases of NPC patients treated with IMRT，including 32 cases of neck node level Ⅳ region which optimized，and a control group of 32 cases which Ⅳ region is still within the CTV；Radiation dose parameters of thyroid were measured using treatment plan system for all patients. These radiation dose parameters of thyroid were compared between optimization and no optimization groups，as well as among different clinical stages， T and N stages， respectively. Meanwhile， a survival analysis was performed using Kaplan-Meier method. Results Reasonably optimizing the neck node level Ⅳ in CTV can significantly reduce the thyroid mean dose and volume percent dose V50（P＜0.05） and does not decrease the local control probability. The thyroid mean dose and V50 of patients with stage Ⅳ were much higher than those with other stages， and for the N0-2 patients， optimization of neck node level Ⅳ in CTV can significantly reduce the thyroid mean dose and V50 comparing with no optimization group. Conclusion For NPC patients， reasonably optimizing the neck node level Ⅳ in CTV is safe and can much better protect the thyroid gland.