非手术肺癌放疗靶区变化的锥形束CT观察

目的 用千伏级锥形束CT (KVCBCT)离线分析非手术肺癌大体肿瘤体积(GTV)随放疗变化规律。
方法 18例患者分为2个组,A组[13例, 依据GTV变化分为A₁(10例)、A₂(3例)组] 常规放疗(1.8~ 2.2 Gy/次),每周治疗前采集1组KVCBCT;B组(5例)加速放疗(5~ 8 Gy/次),每次治疗前采集1组KVCBCT。在治疗计划系统上融合KVCBCT和CT图像后分析GTV变化。
结果 A组GTV缩减>20%者占77%;A₁组在治疗第4周(第20次治疗) GTV递减变化达最大,GTV缩减(0.94±9.94)%,最大缩减－56.76%;A₂组GTV变化与治疗时间无关。B组GTV缩减(－7.41±1.76)%,最大缩减－15.91%,缩减≤10%占71%,GTV随治疗进行变化较小。
结论 GTV变化随治疗进行无统一变化趋势,在第20次治疗时若GTV缩减>20%建议用自适应放疗。

Off-line analysis of gross tumor volume changes in nonoperatively treated lung cancer patients during radiotherapy by kilovoltage cone-beam computed tomography

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 A 1 (n=10) and subgroup A 2 (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 A 1 had the maximum GTV reduction in the 4^th week of treatment (the 20^th treatment);Subgroup A 1 had a mean reduction of (0.94±9.94)%, with a maximum value of －56.76%. Subgroup A 2 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 20^th treatment.