Table_1_Studies of Intra-Fraction Prostate Motion During Stereotactic Irradiation in First Irradiation and Re-Irradiation.docx

BackgroundUnderstanding intra-fractional prostate motions is crucial for stereotactic body radiation therapy (SBRT). No studies have focused on the intra-fractional prostate motions during re-irradiation with SBRT. The objective was to evaluate these translational and rotational motions in primary treated patients and in the context of re-irradiation.
MethodsFrom January 2011 to March 2020, 162 patients with histologically proven prostate cancer underwent prostate SBRT, including 58 as part of a re-irradiation treatment. We used the continuous coordinates of the fiducial markers collected by an orthogonal X-ray dual-image monitoring system. The translations and rotations of the prostate were calculated. Prostate deviations representing overall movement was defined as the length of the 3D-vectors.
ResultsA total of 858 data files were analyzed. The deviations over time in the group of primary treated patients were significantly larger than that of the group of re-irradiation, leading to a mean deviation of 2.73 mm (SD =1.00) versus 1.90 mm (SD =0.79), P<0.001. In the re-irradiation group, we identified displacements of -0.05 mm (SD =1.53), 0.20 mm (SD =1.46); and 0.42 mm (SD =1.24) in the left-right, superior-inferior and anterior-posterior planes. Overall, we observed increasing deviations over the first 30 min followed by a stabilization related to movements in the three translational axes.
ConclusionThis is the first study to focus on intrafraction prostate motions in the context of re-irradiation. We observed that intra-fraction prostate motions persisted in the setting of re-irradiation, although they showed a significant reduction when compared with the first irradiation. These results will help to better estimate random errors during SBRT treatment of intra-prostatic recurrence after irradiation.

### 背景
明确分次内前列腺运动特征对于立体定向体部放射治疗（stereotactic body radiation therapy, SBRT）至关重要。目前尚无针对再放疗SBRT过程中分次内前列腺运动的相关研究。本研究旨在评估初治患者以及再放疗场景下的前列腺平移与旋转运动。

### 方法
2011年1月至2020年3月，共162例经组织学证实的前列腺癌患者接受前列腺SBRT治疗，其中58例为再放疗受试者。我们采用正交X射线双影像监测系统采集的fiducial标记物（fiducial markers）连续坐标，计算前列腺的平移与旋转角度；将反映整体移动的前列腺偏差定义为三维矢量的模长。

### 结果
本研究共分析858份数据文件。初治患者组的随时间变化的前列腺偏差显著高于再放疗组，两组平均偏差分别为2.73 mm（标准差SD=1.00）与1.90 mm（SD=0.79），P<0.001。再放疗组中，左右、头脚、前后平面的位移分别为-0.05 mm（SD=1.53）、0.20 mm（SD=1.46）及0.42 mm（SD=1.24）。整体而言，在前30分钟内偏差随时间逐渐增大，随后在三个平移轴方向的运动趋于稳定。

### 结论
本研究是首个聚焦于再放疗场景下分次内前列腺运动的学术研究。我们发现，尽管与首次放疗相比，再放疗时的分次内前列腺运动幅度显著降低，但该运动仍然存在。本研究结果有助于更精准地评估放疗后前列腺内复发患者接受SBRT治疗时的随机误差。