A dosimetric comparison of volumetric modulated Arc therapy with conventional intensity-modulated radiotherapy for breast cancer radiotherapy after breast-conserving surgery / 中华放射医学与防护杂志

ABSTRACT

Objective To compare the dosimetric differences between two plans of RapidArc and 5F-IMRT for breast cancer radiotherapy after breast-conserving surgery.Methods Eight female patients with left-sided breast cancer after breast-conserving surgery were selected.A dose of 50 Gy in 25 fractions was prescribed for plans of RapidArc and 5F-IMRT.Target conformity index (CI),homogeneity index (HI),target coverage,exposure dose volume delivered to organ at risk were compared between two plans.At the same time,treatment delivery time and monitor units (MU) were also compared.Results The target conformity index (CI) in RapidArc plan (·0.88 ±0.03) was higher than that in 5F-IMRT plan (0.79 ±0.02,t =8.28,P ＜ 0.05).The homogeneity index (HI) in RapidArc plan 9.01 ± 0.73 was significantly lower than that in 5F-IMRT plan10.44 ± 1.08 (t =-2.73,P ＜0.05).For the dose volume delivered to the ipsilateral lung in two plans,the values of V10,V20,V30,and Dmean in RapidArc plan were lower than those in 5F-IMRT plan(t =-7.53,-7.20,-8.39,-7.80,P ＜ 0.05).However,the value of V5 in RapidArc plan was higher than that in 5F-IMRT plan (t =5.67,P ＜0.05).For the heart,the values of V5,V10 and Dmean in RapidArc plan were higher than those in IMRT plan(t =10.46,28.76,5.40,P ＜ 0.05),while the value of V30 in RapidArc plan was lower than that in 5F-IMRT plan(t =-6.12,P ＜0.05).The values of V5 in contralateral lung and breast were higher in RapidArc plan than those in 5F-IMRT plan(lungt =21.50,P ＜0.05;breastt =5.44,P ＜0.05).The MU in RapidArc plan was decreased by 25％,and the average treatment delivery time was saved by 60％,compared with that of 5F-IMRT plan.Conclusions During breast cancer radiotherapy after breast-conserving surgery,compared with 5F-IMRT plan,the RapidArc plan could improve the target HI,and reduce both the irradiated dose in high-dose volume and MU,and shorten the treatment time,but increased the exposed volume in low-dose volume of normal tissues.