Bell Linda J, Cox Jennifer, Eade Thomas, Rinks Marianne, Kneebone Andrew
Northern Sydney Cancer Centre, Radiation Oncology Department, Royal North Shore Hospital, Australia; Faculty of Health Sciences, University of Sydney, Sydney, New South Wales, Australia.
J Med Imaging Radiat Oncol. 2013 Dec;57(6):725-32. doi: 10.1111/1754-9485.12089. Epub 2013 Jul 9.
There is little data to guide radiation oncologists on appropriate margin selection in the post-prostatectomy setting. The aim of this study was to quantify interfraction variation in motion of the prostate bed to determine these margins.
The superior and inferior surgical clips in the prostate bed were tracked on pretreatment cone beam CT images (n = 377) for 40 patients who had received post-prostatectomy radiotherapy. Prostate bed motion was calculated for the upper and lower segments by measuring the position of surgical clips located close to midline relative to bony anatomy in the axial (translational) and sagittal (tilt) planes. The frequency of potential geographic misses was calculated for either 1 cm or 0.5 cm posterior planning target volume margins.
The mean magnitude of movement of the prostate bed in the anterior-posterior, superior-inferior and left-right planes, respectively, were as follows: upper portion, 0.50 cm, 0.28 cm, 0.10 cm; lower portion, 0.18 cm, 0.18 cm, 0.08 cm. The random and systematic errors, respectively, of the prostate bed motion in the anterior-posterior, superior-inferior and left-right planes, respectively, were as follows: upper portion, 0.47 cm and 0.50 cm, 0.28 cm and 0.27 cm, 0.11 cm and 0.11 cm; lower portion, 0.17 cm and 0.18 cm, 0.17 cm and 0.19 cm, 0.08 cm and 0.10 cm. Most geographic misses occurred in the upper prostate bed in the anterior-posterior plane. The median prostate bed tilt was 1.8° (range -23.4° to 42.3°).
Variability was seen in all planes for the movement of both surgical clips. The greatest movement occurred in the anterior-posterior plane in the upper prostate bed, which could cause geographic miss of treatment delivery. The variability in the movement of the superior and inferior clips indicates a prostate bed tilt that would be difficult to correct with standard online matching techniques. This creates a strong argument for using anisotropic planning target volume margins in post-prostatectomy radiotherapy.
在前列腺切除术后的情况下，几乎没有数据可指导放射肿瘤学家进行合适的边缘选择。本研究的目的是量化前列腺床运动的分次间变化，以确定这些边缘。
在接受前列腺切除术后放疗的40例患者的治疗前锥形束CT图像（n = 377）上追踪前列腺床内的上下手术夹。通过测量轴向（平移）和矢状（倾斜）平面中靠近中线的手术夹相对于骨骼解剖结构的位置，计算前列腺床上段和下段的运动。计算1 cm或0.5 cm后计划靶体积边缘的潜在几何遗漏频率。
前列腺床在前后、上下和左右平面的平均移动幅度分别如下：上段，0.50 cm、0.28 cm、0.10 cm；下段：0.18 cm、0.18 cm、0.08 cm。前列腺床在前后、上下和左右平面运动的随机误差和系统误差分别如下：上段，0.47 cm和0.50 cm、0.28 cm和0.27 cm、0.11 cm和0.11 cm；下段，0.17 cm和0.18 cm、0.17 cm和0.19 cm、0.08 cm和0.10 cm。大多数几何遗漏发生在前后面的前列腺床上段。前列腺床的中位倾斜度为1.8°（范围-23.4°至42.3°）。
两个手术夹的运动在所有平面上均存在变异性。最大的运动发生在前后面的前列腺床上段，这可能导致治疗投照的几何遗漏。上下手术夹运动的变异性表明前列腺床倾斜，这很难用标准的在线匹配技术校正。这有力地支持了在前列腺切除术后放疗中使用各向异性的计划靶体积边缘。
