Ruben J D, Seeley A, Panettieri V, Ackerly T
Department of Surgery, Monash University, Melbourne, Australia; William Buckland Radiotherapy Centre, The Alfred Hospital, Prahran, Australia.
William Buckland Radiotherapy Centre, The Alfred Hospital, Prahran, Australia.
Clin Oncol (R Coll Radiol). 2016 Jan;28(1):21-7. doi: 10.1016/j.clon.2015.08.010. Epub 2015 Oct 1.
To investigate variation in tumour breathing motion (TBM) between the planning four-dimensional computed tomograph (4DCT) and treatment itself for primary or secondary lung tumours undergoing stereotactic ablative radiotherapy (SABR).
Sixteen consecutive patients underwent planning 4DCT at least 1 week after implantation of a fiducial marker. The maximal extent of breathing motion of the intra-tumoural fiducial was measured at 4DCT and again at delivery of each SABR fraction on the linac using stereoscopic kilovoltage imaging. Displacements of the fiducial beyond planned limits were measured in three dimensions and represented as vectors. Variation in breathing motion between the planning 4DCT and treatment, and between individual SABR fractions was analysed.
Although TBM at treatment exceeded planned tumour motion limits for at least part of the course for all patients, 31% of patients remained consistently within 1 mm, 50% within 2 mm and 69% consistently within 3 mm of planned parameters. However, 19% of patients experienced TBM variation 5 mm or more beyond planned limits for at least one fraction. For all patients, the median displacement vector at treatment beyond the planned motion envelope was 1.0 mm (mean 2.0 mm, range 0-12.7 mm). Variation in TBM at treatment from 4DCT correlated neither with the magnitude of TBM at 4DCT nor with planning target volume size (rs = 0.13, P = 0.62; rs = 0.02, P = 0.94, respectively). Nor was TBM variation related to tumour type or lobar position (P = 0.35, P = 0.06, respectively). Inter-fraction TBM variation was modest, with an average standard deviation of 1.7 mm (0.3-8.7 mm).
TBM variation between 4DCT and treatment and between SABR fractions was modest for most patients. However, 19% of patients experienced significant TBM variation that could be clinically relevant for those most severely affected. It seems prudent to carry out on-couch assessment of TBM at each SABR fraction to identify such patients who might benefit from respiratory gating or adaptive radiotherapy to maintain tumour motion within the planned limits.
研究接受立体定向消融放疗（SABR）的原发性或继发性肺肿瘤患者，在计划四维计算机断层扫描（4DCT）与治疗过程中肿瘤呼吸运动（TBM）的差异。
16例连续患者在植入基准标记物至少1周后进行计划4DCT检查。在4DCT时测量瘤内基准标记物的最大呼吸运动范围，并在直线加速器上每次SABR分次治疗时再次使用立体千伏成像进行测量。测量基准标记物超出计划限度的三维位移，并表示为向量。分析计划4DCT与治疗之间以及各个SABR分次之间呼吸运动的差异。
尽管所有患者在治疗过程中至少部分时间的TBM超过了计划的肿瘤运动限度，但31%的患者始终保持在计划参数的1毫米范围内，50%在2毫米范围内，69%始终在3毫米范围内。然而，19%的患者至少有一个分次的TBM变化超出计划限度5毫米或更多。对于所有患者，治疗时超出计划运动范围的中位位移向量为1.0毫米（平均2.0毫米，范围0 - 12.7毫米）。治疗时TBM相对于4DCT的变化，既与4DCT时TBM的大小无关，也与计划靶体积大小无关（分别为rs = 0.13，P = 0.62；rs = 0.02，P = 0.94）。TBM变化也与肿瘤类型或叶位置无关（分别为P = 0.35，P = 0.06）。分次间TBM变化较小，平均标准差为1.7毫米（0.3 - 8.7毫米）。
对于大多数患者，4DCT与治疗之间以及SABR分次之间的TBM变化较小。然而，19%的患者经历了显著的TBM变化，这对于受影响最严重的患者可能具有临床相关性。在每次SABR分次治疗时对TBM进行床旁评估，以识别那些可能从呼吸门控或自适应放疗中获益从而将肿瘤运动维持在计划限度内的患者，似乎是谨慎的做法。
