A dose volume analysis of brain stem injury after intensity-modulated radiotherapy in patients with nasopharyngeal carcinoma / 中华放射肿瘤学杂志

ABSTRACT

Objective To investigate the relationship between the incidence of radiation-induced brain stem injury after intensity-modulated radiotherapy (IMRT) and the radiation dose volume in patients with nasopharyngeal carcinoma.Methods A retrospective analysis was performed on the data of 258 patients newly diagnosed with nasopharyngeal carcinoma who received IMRT in our group from 2005 to 2013.The radiation dose per unit volume of brain stem was analyzed.The relationship between the incidence of brain stem injury induced by IMRT and the radiation dose volume was studied.The survival rate was calculated using the Kaplan-Meier method.The factors influencing the radiation-induced brain stem injury were analyzed using the Cox regression model.Results Two patients with stage T3 disease and three patients with T4 disease had radiation-induced brain stem injury.The 3-and 5-year injury incidence rates were 1.6％ and 2.4％,respectively.The latency ranged between 9 and 58 months,with a median latency of 19 months.The median D1％ and Dmax for the brain stem were 54.24 and 59.22 Gy in all patients,54.31 and 59.45 Gy in patients with stage T3 disease,and 61.29 and 66.37 Gy in patients with stage T4 disease,respectively.In the five patients with brain stem injury,the D1％ and Dmax were larger than 60 and 63 Gy,respectively.The univariate analysis showed that the incidence of radiation-induced brain stem injury was correlated with D1％,Dmax,D0.1 cm3,D0.5 cm3,and D1.0 cm3 (all P=0.01).The incidence of radiation-induced brain stem injury was significantly lower in patients with D1％,Dmax,D0.1 cm3,D0.5 cm3,and D1.0 cm3 no larger than 60,63,60,58,and 56 Gy,respectively (all P =0.00).Conclusions The incidence of radiation-induced brain stem injury after IMRT is relatively low in patients with nasopharyngeal carcinoma.Strict control of the dose to the brain stem may help to reduce the incidence of brain stem injury and improve the long-term quality of life.