Patel Rakesh R, Orton Nigel, Tomé Wolfgang A, Chappell Rick, Ritter Mark A
Department of Radiation Oncology, University of Wisconsin, 600 Highland Avenue K4/B100, Madison, WI 53792, USA.
Radiother Oncol. 2003 Jun;67(3):285-94. doi: 10.1016/s0167-8140(03)00056-2.
To compare the rectal wall and bladder volume in the high dose region with or without the use of a balloon catheter with both three-dimensional (3D)-conformal and intensity modulated radiation therapy (CRT, IMRT) approaches in the treatment of prostate cancer.
Five patients with a wide range of prostate volumes and treated with primary external beam radiation therapy for localized prostate cancer were selected for analysis. Pinnacle treatment plans were generated utilizing a 3D conformal six-field design and an IMRT seven coplanar-field plan with a novel, three-step optimization and with ultrasound localization. Separate plans were devised with a rectal balloon deflated or air inflated with and without inclusion of the seminal vesicles (SV) in the target volume. The prescription dose was 76Gy in 38 fractions of 2Gy each. Cumulative dose-volume histograms (DVHs) were analyzed for the planning target volume (PTV), rectal wall, and bladder with an inflated (60cc air) or deflated balloon with and without SV included. The volumes of rectal wall and bladder above 60, 65, and 70Gy with each treatment approach were evaluated.
Daily balloon placement was well-tolerated with good patient positional reproducibility. Inflation of the rectal balloon in all cases resulted in a significant decrease in the absolute volume of rectal wall receiving greater than 60, 65, or 70Gy. The rectal sparing ratio (RSR), consisting of a structure's high dose volume with the catheter inflated, divided by the volume with the catheter deflated, was calculated for each patient with and without seminal vesicle inclusion for 3D-CRT and IMRT. For 3D-CRT, RSRs with SV included were 0.59, 0.59, and 0.56 and with SV excluded were 0.60, 0.58, and 0.54 at doses of greater than 60, 65, and 70Gy, respectively. Similarly, for IMRT, the mean RSRs were 0.59, 0.59, and 0.63 including SV and 0.71, 0.66, and 0.67 excluding SV at these same dose levels, respectively. Averaged over all conditions, inflation of the rectal balloon resulted in a significant reduction in rectal volume receiving > or =65Gy to a mean ratio of 0.61 (P=0.01) or, in other words, a mean fractional high dose rectal sparing of 39%. There was a slight overall increase to 1.13 in the relative volume of bladder receiving at least 65Gy; however, this was not significant (P=0.6). Use of an endorectal balloon with a non-image-guided 3D-CRT plan produced about as much rectal dose sparing as a highly conformal, image-guided IMRT approach without a balloon. However, inclusion of a balloon with IMRT produced further rectal sparing still.
These results indicate that use of a rectal balloon with a 3D-CRT plan incorporating typical treatment margins will produce significant high dose rectal sparing that is comparable to that achieved by a highly conformal IMRT with ultrasound localization. Further sparing is achieved with the inclusion of a balloon catheter in an IMRT plan. Thus, in addition to a previously reported advantage of prostate immobilization, the use of a rectal displacement balloon during daily treatment results in high dose rectal wall sparing during both modestly and highly conformal radiotherapy. Such sparing could assist in controlling and limiting rectal toxicity during increasingly aggressive dose escalation.
比较在前列腺癌治疗中，采用三维（3D）适形放疗和调强放疗（CRT、IMRT）方法时，使用或不使用球囊导管情况下高剂量区域的直肠壁和膀胱体积。
选取5例前列腺体积范围较广且接受局部前列腺癌初次外照射放疗的患者进行分析。利用3D适形六野设计和IMRT七共面野计划生成Pinnacle治疗计划，采用新颖的三步优化法并结合超声定位。分别设计直肠球囊放气或充气且靶区包含或不包含精囊（SV）的计划。处方剂量为76Gy，分38次，每次2Gy。分析计划靶区（PTV）、直肠壁和膀胱在球囊充气（60cc空气）或放气且包含或不包含SV情况下的累积剂量体积直方图（DVH）。评估每种治疗方法下直肠壁和膀胱在60、65和70Gy以上的体积。
每日放置球囊耐受性良好，患者体位重复性佳。所有病例中直肠球囊充气均导致接受大于60、65或70Gy的直肠壁绝对体积显著减小。计算每位患者在3D - CRT和IMRT中包含或不包含精囊时的直肠 sparing比（RSR），即球囊充气时结构的高剂量体积除以球囊放气时的体积。对于3D - CRT，在大于60、65和70Gy剂量时，包含SV的RSR分别为0.59、0.59和0.56，不包含SV的分别为0.60、0.58和0.54。同样，对于IMRT，在相同剂量水平下，包含SV时平均RSR分别为0.59、0.59和0.63，不包含SV时分别为0.71、0.66和0.67。在所有情况下平均，直肠球囊充气使接受≥65Gy的直肠体积显著减小至平均比例0.61（P = 0.01），换句话说，直肠高剂量部分平均 sparing为39%。接受至少65Gy的膀胱相对体积总体略有增加至1.13；然而，这不显著（P = 0.6）。使用非图像引导的3D - CRT计划并结合直肠内球囊产生的直肠剂量 sparing与不使用球囊的高度适形图像引导IMRT方法相当。然而，IMRT中使用球囊仍能进一步减少直肠剂量。
这些结果表明，在包含典型治疗边界的3D - CRT计划中使用直肠球囊可产生显著的高剂量直肠 sparing，与采用超声定位的高度适形IMRT相当。在IMRT计划中加入球囊导管可进一步减少剂量。因此，除了先前报道的前列腺固定优势外，在日常治疗中使用直肠移位球囊可在适度和高度适形放疗期间实现高剂量直肠壁 sparing。这种 sparing有助于在日益激进的剂量递增过程中控制和限制直肠毒性。
