Comparative study of treatment planning between intensity - modulated arc therapy and simultaneously integrated boost intensity-modulated radiotherapy in nasopharyngeal carcinoma / 中华放射肿瘤学杂志

ABSTRACT

Objective To compare the dosimetric differences of target volume and organ at risk between intensity-modulated arc therapy (IMAT) and simultaneously integrated boost intensity-modulated radiotherapy (SIB-IMRT) in nasopharyngeal carcinoma. Methods IMAT and SIB-IMRT treatment plans of 10 nasopharyngeal carcinoma cases were generated by Varian Eclipse ver8. 6 treatment planning system. The dosimetric parameters of target volume and organ at risk (OAR), the monitor units (MU) and treatment time were compared between IMAT and SIB-IMRT treatment plan. Results The conformal index ( CI ) of PTV, PTV1, PTV2 of IMAT and SIB-IMRT were 0. 71 and 0. 75 ( Z = - 2. 32, P ＜ 0. 05 ), 0. 54 and 0. 59 (Z= -2.56,P＜0.05), 0.71 and 0.78(Z= -2.52,P＜0.05), respectively. the homogenous index (HI) of PTV, PTV1, PTV2 of IMAT and SIB-IMRT were 10.5 and 11.2(Z= -0. 84,P＞0.05),13. 1 and 17. 1(Z= -1.68,P＞0.05) and 14. 1 and 13.3(Z= -1. 01,P＞0.05) respectively;the brain-stem mean does were 3512. 8 cGy ± 406. 2 cGy and 3384. 3 cGy ± 361.3 cGy ( Z= - 1.82, P ＞ 0. 05 ); the brain-stem maximum dose were 5528. 1cGy ± 192. 9 cGy and 5727. 5 cGy ± 356. 3 cGy ( Z = - 1.12, P ＞ 0. 05 ); the maximum dose of spinal-cord were were 4186. 1cGy ± 88.7 cGy and 4390. 2 cGy ± 74. 9 cGy ( Z =-2. 38 ,P ＜ 0. 05 ). There were no significant differences between parotid dose and normal tissue ( P ＞0. 05. ) MU were 606 ± 96 and 1308 ± 213 for IMAT and SIB-IMRT ( Z= - 2. 52, P ＜ 0. 05 ). Conclusions The IMAT plan showed a better conformal index than SIB-IMRT plan, with the same dosimetric parameters of the target volume and OAR. The IMAT plan could reduce normal tissues dose, monitor units and treatment time in the treatment of nasopharyngeal carcinoma.