Fiorino Claudio, Foppiano Franca, Franzone Paola, Broggi Sara, Castellone Pietro, Marcenaro Michela, Calandrino Riccardo, Sanguineti Giuseppe
Servizio di Fisica Sanitaria, IRCCS H. S. Raffaele, Via Olgettina 60, 20132 Milano, Italy.
Radiother Oncol. 2005 Feb;74(2):187-95. doi: 10.1016/j.radonc.2004.10.002. Epub 2004 Oct 28.
To investigate the extent and the impact of rectum and bladder motion during adjuvant conformal radiotherapy (3DCRT) after radical prostatectomy (RP).
Nine patients previously operated with RP and treated with early adjuvant 3DCRT were considered for this investigation. Weekly CT scans were collected during treatment (CT1-CTn, n=4-6) and were 3D matched using bony anatomy with the planning CT (CT0). A single observer drew the contours of rectum and bladder on all CTs. The CTV (prostate+/-seminal vesicles surgical bed) was contoured on CT0 by a single observer and a 4-field 3DCRT technique was planned: dose statistics/dose-volume histograms (DVH) of the rectum and bladder were calculated for each contour referred to CT0, CT1...CTn. Average DVHs during the treatment were then calculated and compared with the planned DVH. Cranial, caudal, anterior and posterior shifts of rectum and bladder were also assessed by lateral BEV projections. NTCP values for the rectum were also calculated using the Lyman-Kutcher model.
Random variations of volume and DVHs due to variable filling content were found for the bladder; a trend of the bladder to be more empty during therapy with respect to CT0 was also found (median values: 45 cm3 vs. 79 cm3, P=0.02). Regarding the rectum, 6/9 patients showed an average DVH 'worse' than the planned one (up to 10-20%). BEV and volume analyses showed that the rectal volume decreased in 3/9 patients after the first week. In 6/9 patients a systematic anterior shift of the cranial half of the rectum was detected and found to be correlated with a corresponding shift of the posterior border of CTV contoured by five different observers. The average rectal NTCP during therapy was systematically higher than the NTCP referred to CT0 (average increase 1.2%; range 0.0-3.7%, for a 70 Gy ICRU dose, P=0.01).
The impact of systematic uncertainty due to rectal wall motion seems to be relatively high for patients treated with adjuvant 3DCRT after RP. The detected trend of the rectum in migrating anteriorly during therapy is consistent with post-surgery settlement effects and/or some modification of rectum mobility due to irradiation. Rectal motion (and consequent shifts of CTV) was large at the half cranial portion of the rectum while it was very small below the flexure.
探讨根治性前列腺切除术后辅助适形放疗（3DCRT）期间直肠和膀胱运动的程度及其影响。
本研究纳入9例曾接受根治性前列腺切除术并接受早期辅助3DCRT治疗的患者。在治疗期间每周收集CT扫描图像（CT1 - CTn，n = 4 - 6），并使用骨解剖结构与计划CT（CT0）进行三维匹配。由一名观察者在所有CT图像上勾画直肠和膀胱的轮廓。由一名观察者在CT0上勾画临床靶区（前列腺±精囊腺手术床），并制定四野3DCRT技术计划：计算直肠和膀胱相对于CT0、CT1……CTn的每个轮廓的剂量统计/剂量体积直方图（DVH）。然后计算治疗期间的平均DVH，并与计划的DVH进行比较。还通过侧位BEV投影评估直肠和膀胱的头侧、尾侧、前侧和后侧移位。使用Lyman - Kutcher模型计算直肠的正常组织并发症概率（NTCP）值。
发现膀胱因充盈内容物变化而导致体积和DVH的随机变化；还发现治疗期间膀胱相对于CT0有更空虚的趋势（中位数：45 cm³ 对 79 cm³，P = 0.02）。关于直肠，6/9的患者显示平均DVH比计划的“更差”（高达10 - 20%）。BEV和体积分析显示，3/9的患者在第一周后直肠体积减小。在6/9的患者中检测到直肠头侧半部有系统性的向前移位，并且发现与由五名不同观察者勾画的CTV后边界的相应移位相关。治疗期间直肠的平均NTCP系统性地高于CT0时的NTCP（对于70 Gy的ICRU剂量，平均增加1.2%；范围0.0 - 3.7%，P = 0.01）。
对于根治性前列腺切除术后接受辅助3DCRT治疗的患者，直肠壁运动导致的系统性不确定性影响似乎相对较高。治疗期间检测到的直肠向前迁移趋势与术后沉降效应和/或放疗导致的直肠活动度的某些改变一致。直肠运动（以及随之而来的CTV移位）在直肠头侧半部较大，而在弯曲以下则非常小。
