Georg Petra, Georg Dietmar, Hillbrand Martin, Kirisits Christian, Pötter Richard
Department of Radiotherapy and Radiobiology, Medical University Vienna/AKH Vienna, Austria.
Radiother Oncol. 2006 Jul;80(1):19-26. doi: 10.1016/j.radonc.2006.04.014. Epub 2006 Jun 12.
To evaluate the influence of uterus and bladder size on large and small bowel sparing with intensity modulated whole pelvic radiotherapy (IM-WPRT) in gynecologic patients.
Twenty patients were selected; 10 women with cervical cancer treated with definitive radiotherapy (group 'DEF') and 10 endometrial cancer patients treated postoperatively (group 'POST'). Bladder, rectal wall, small (SB) and large bowel (LB) were delineated as organs at risk. A conformal four field technique and a seven field IMRT plan (prescription dose 50.4 Gy) were compared in terms of DVH and various target parameters.
At doses between 40 and 50.4 Gy statistically significant improvements (P<0.05) were observed for IM-WPRT for irradiated volume of rectal wall and bladder. In both patient groups, with IMRT the average irradiated volume of SB was reduced by a factor of 6 at 50.4Gy. This ratio was 2 for LB. In the DEF group the effect of SB-sparing with IMRT correlated with bladder size (correlation coefficient 0.70) while it did not correlate in the postoperative group. The effect of LB-sparing decreased with increasing bladder size in both groups but the impact of IMRT was larger for postoperative patients.
IMRT significantly reduced the absolute volume of rectal wall, bladder and bowel irradiated at the prescribed dose level in gynaecologic patients. Main differences between POST and DEF patients receiving IM-WPRT were absolute volumes of LB irradiated to doses between 35 and 50Gy, suggesting an impact of intact uterus on LB volume in the pelvis. POST patients seem to benefit most from elective nodal IMRT. Bladder filling is an important co-factor influencing the benefit of IMRT with respect to OAR sparing.
评估子宫和膀胱大小对妇科患者调强全盆腔放疗（IM-WPRT）时大小肠受量的影响。
选取20例患者；10例接受根治性放疗的宫颈癌女性患者（“DEF”组）和10例术后子宫内膜癌患者（“POST”组）。将膀胱、直肠壁、小肠（SB）和大肠（LB）划定为危及器官。比较了适形四野技术和七野调强放疗计划（处方剂量50.4 Gy）的剂量体积直方图（DVH）及各种靶区参数。
在40至50.4 Gy剂量之间，IM-WPRT在直肠壁和膀胱的照射体积方面有统计学显著改善（P<0.05）。在两组患者中，采用调强放疗时，50.4 Gy时SB的平均照射体积减少了6倍。LB的这一比例为2倍。在DEF组中，调强放疗对SB的保护效果与膀胱大小相关（相关系数0.70），而在术后组中则无相关性。两组中LB的保护效果均随膀胱大小增加而降低，但调强放疗对术后患者的影响更大。
调强放疗显著降低了妇科患者在规定剂量水平下直肠壁、膀胱和肠道的绝对受照体积。接受IM-WPRT的POST组和DEF组患者之间的主要差异在于35至50 Gy剂量照射的LB绝对体积，提示完整子宫对盆腔LB体积有影响。POST组患者似乎从选择性淋巴结调强放疗中获益最大。膀胱充盈是影响调强放疗对危及器官保护效果的重要协同因素。
