Off-line analysis of gross tumor volume changes in nonoperatively treated lung cancer patients during radiotherapy by kilovoltage cone-beam computed tomography / 中华放射肿瘤学杂志

ABSTRACT

Objective To investigate the gross tumor volume (GTV) changes in nonoperatively treated lung cancer patients during radiotherapy by off-line analysis using kilovoltage cone-beam computed tomography (KVCBCT).Methods Eighteen nonoperatively treated lung cancer patients were divided into group A (n =13) to receive conventional radiotherapy (1.8-2.2 Gy/fraction) and group B (n =5) to receive accelerated radiotherapy (5-8 Gy/fraction).Group A was further divided into subgroup A1 (n =10) and subgroup A2 (n =3) according to GTV changes.Each patient in group A underwent KVCBCT scan before treatment once a week,and each patient in group B underwent KVCBCT scan before each treatment.KVCBCT and CT images were registered in the treatment planning system to analyze GTV changes.Results Of all patients in group A,77％ showed ＞ 20％ GTV reduction.Subgroup A1 had the maximum GTV reduction in the 4th week of treatment (the 20th treatment) ;Subgroup A1 had a mean reduction of (0.94 ± 9.94)％,with a maximum value of-56.76％.Subgroup A2 showed no correlation between GTV changes and treatment time.Group B had a mean GTV reduction of (-7.41 ± 1.76)％,with a maximum value of -15.91％.Of all patients in group B,71％ showed ≤ 10％ GTV reduction.Small GTV changes were observed in group B.Conclusions There are no regular GTV changes in nonoperatively treated lung cancer patients during radiotherapy.Adaptive radiotherapy is recommended in the cases where GTV is reduced over 20％ in the 20th treatment.