A dosimetric comparison of volumetric modulated arc therapy with fixed-fields intensity modulated radiotherapy for ⅠE and ⅡE nasal NK/T-cell lymphoma / 中华放射医学与防护杂志

ABSTRACT

Objective To investigate the dosimetric characteristics and their clinical applications of volumetric modulated Arc therapy (RapidArc) with fixed-fields intensity modulated radiotherapy for early stage nasal NK/T-cell lymphoma.Methods Ten patients with stage Ⅰ E and Ⅱ E nasal NK/T-cell lymphoma were enrolled in the study.Five field coplanar plan (5F),nine field coplanar plan (9F),five field non-coplanar plan (5F-N) and RapidArc plans were designed for each patient,in which 5F plan was set as the control group.Conformity index (CI) and homogeneity index (HI) as well as the maximum dose of organs at risks were compared.Results The target CI of 5F,9F,5F-N and RapidArc plan was 0.419±0.159,0.478 ±0.181,0.465 ±0.121 and 0.518 ±0.111,respectively.Compared with 5F (0.136±0.038),the target HI of 9F and RapidArc plan was 0.111 ±0.027 and 0.112 ±0.031 (t =3.11,3.04,P ＜ 0.05).9F plan significantly increased the Dmax of lens in the contralateral side(t =2.82,P ＜ 0.05) and in ipsilateral side (t =3.25,P ＜ 0.05),while 5F-N plan decreased the Dmax of optical nerves by up to 9％.RapidArc plan effectively reduced the radiation to organs at risk in lens (t =3.25,P ＜0.05),eyes (t =3.25,P ＜0.05),optical nerve (t =2.57,P ＜0.05) and optical chaism(t =7.62,P ＜0.05).The delivery efficiency of four plans ranked as RapidArc ＞ 5F ＞ 5F-N ＞ 9F.Conclusions RapidArc produced statistically significant improvement in the dose distributions of targets,and also reduced the Dmax of organs at risk,which would be the better choice of radiotherapy for nasal NK/T-cell lymphoma.