A split-GTV delineation approach for dose optimisation for intensity-modulated radiotherapy for advanced T-stage nasopharyngeal carcinoma with prevertebral space involvement / 中国医师杂志

ABSTRACT

Objective To explore the dosimetric effect of using a split of the gross tumor volume (GTV) delineation approach during intensity-modulated radiotherapy (IMRT) treatment planning for advanced T-stage nasopharyngeal carcinoma (NPC) with prevertebral space involvement (PSI).Methods Twenty NPC patients with T3-T4 tumors with prevertebral space involvement were studied.Two kinds of plans were generated based on the same protocol.The first plan was GTV-split consisting of organ at risk (including spine cord and brain stem) overlapping and non-overlapping subsegments.The subsegments were assigned independent dose constraint.The second plan was done based on a standard treatment planning protocol.The two plans were compared with respect to target coverage and organ at risk (OAR) sparing,and target conformity index.Results Two plans both met requirement of dose coverage of target and constraints on normal tissue.Regarding the planning gross target volume (PGTV),the doses of ＜ 93％ volume of plan 1 and plan 2 were [(0.63 ± 0.21)％,and (0.68 ± 0.10)％,P =0.049];the doses of ＞ 110％ volume of plan 1 and plan 2 were [(11.59 ± 7.Ol) ％,and (12.71 ± 6.03) ％,P =0.041];the doses of ＞115％ volume of plan 1 and plan 2 were [(2.05 ± 0.80)％,and (2.76 ± 1.14)％,P =0.049];about OARs,the maximal dose of spine cord for plan 1 and plan 2 were (41.00 ± 4.52) Gy and (45.00 ± 3.25) Gy (P =0.048);and the target coverage and target conformity index of plan 1 were better than those of plan 2,the p-values were 0.063,and 0.135,respectively.The difference between two plans was statistically significant (P ＜ 0.05).Conclusions A split-GTV delineation,independent dose constraint,and multi-course IMRT for advanced T-stage nasopharyngeal carcinoma with prevertebral space involvement optimized IMRT treatment planning,improved target coverage and target conformity index,and decreased the maximal dose for the spine cord and brain stem.It is feasible and has advantage to decrease the dose to OARs.The approach deserves to be further studied.