Target setup margin and dose evaluation for cervical cancer cases based on the off-line adaptive radiotherapy / 中华放射医学与防护杂志

ABSTRACT

Objective To study the target setup margin and dose evaluation for cervical cancer patients with volume-modulated arc therapy in the off-line adaptive radiation therapy (off-line ART),Methods A total of fifty patients with cervical cancer were randomly divided into test group and control group.Cone beam CT scanning was performed twice a week,the setup errors in directions of LR,AP and CC were recorded in the whole treatment process.The target setup formula was used to calculate the new CTV-PTV setup margin.At the same time,the setup error was returned to planning isocenter (ISO).For the control group,the dose was recalculated on the basis of the original PTV after considering ISO shift.For the test group,the dose was also recalculated after the new extended boundary of the target.The dosimetric parameters of CTV and organs at risk (OAR) were evaluated between two groups after dose recalculation.Results According to the target setup formula,extended boundaries of CTV in the direction of LR,AP,CC were 0.45,0.46 and 0.82 cm,respectively.The test group increased in CTV with D100％ and D95％ (t =-8.16,-6.73,P ＜0.05) and decreased in femoral head with V40,V30 and D (t=3.14,-9.52,-7.48,P＜0.05) than the control group.The test group decreased in the pelvis with V34 and D than control group (t =10.14,-9.38,P ＜0.05).Conclusions The CTV-PTV setup margin and the dose of OAR were effectively reduced,and the coverage of target area was extended when the off-line ART technology was conducted in the volume-modulated arc therapy for cervical cancer.