Intensity modulated radiation therapy (IMRT): differences in target volumes and improvement in clinically relevant doses to small bowel in rectal carcinoma.
Intensity modulated radiation therapy (IMRT): differences in target volumes and improvement in clinically relevant doses to small bowel in rectal carcinoma.
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DOI：
10.1186/1748-717x-6-63
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发表时间：
2011-06-08
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影响因子：
--
通讯作者：
Das P
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文献类型：
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作者：
Mok H;Crane CH;Palmer MB;Briere TM;Beddar S;Delclos ME;Krishnan S;Das P
在接受低至中剂量辐射的小肠数量与急性、严重胃肠道毒性（主要是腹泻）的发生率之间存在着很强的剂量-体积关系。有相当大的兴趣在应用高度适形治疗方法，如调强放射治疗（IMRT），以减少剂量相邻器官的风险在治疗直肠癌。因此，我们进行了一个全面的剂量学评价调强放射治疗相比，三维适形放射治疗（3DCRT）的标准，术前治疗直肠癌。使用RTOG共识肛门直肠轮廓指南，为10名在我们的研究机构接受直肠癌术前治疗的患者生成治疗体积，将IMRT计划与经典解剖标志的计划以及治疗RTOG共识体积的3DCRT计划进行比较。患者均为T3，淋巴结阴性（N = 1）或淋巴结阳性（N = 9），计划总剂量为45-戈伊。IMRT和3DCRT计划之间的剂量体积直方图参数进行了成对比较。与3DCRT相比，IMRT计划在治疗大体疾病和高危淋巴结体积方面具有更好的上级PTV覆盖率、剂量均匀性和适形性。此外，与3DCRT计划相比，IMRT实现了肠道剂量的同时减少（小肠平均剂量：18.6-戈伊对比25.2-戈伊3DCRT; p = 0.005），膀胱（V40 Gy：56.8% IMRT vs 75.4% 3DCRT; p = 0.005），骨盆骨（V40 Gy：47.0%IMRT vs 56.9%3DCRT; p = 0.005），股骨头（V40Gy：3.4%IMRT vs 9.1%3DCRT; p = 0.005），接受已知可诱导临床相关急性毒性的剂量水平的小肠绝对体积有所改善（小肠V15 Gy：138-cc IMRT与157-cc 3DCRT; p = 0.005）。我们发现，调强放射治疗体积通常大于经典的骨标志衍生领域，而不会招致惩罚与相邻器官的风险。对于直肠癌，调强放射治疗，与三维适形放疗相比，在靶区覆盖、均匀性和适形性方面产生了上级计划，同时降低了对邻近危险器官的剂量。尽管治疗体积较大，这是实现的，提高了通过使用腹部板装置的IMRT的治疗率的临床相关的改善的可能性。
A strong dose-volume relationship exists between the amount of small bowel receiving low- to intermediate-doses of radiation and the rates of acute, severe gastrointestinal toxicity, principally diarrhea. There is considerable interest in the application of highly conformal treatment approaches, such as intensity-modulated radiation therapy (IMRT), to reduce dose to adjacent organs-at-risk in the treatment of carcinoma of the rectum. Therefore, we performed a comprehensive dosimetric evaluation of IMRT compared to 3-dimensional conformal radiation therapy (3DCRT) in standard, preoperative treatment for rectal cancer. Using RTOG consensus anorectal contouring guidelines, treatment volumes were generated for ten patients treated preoperatively at our institution for rectal carcinoma, with IMRT plans compared to plans derived from classic anatomic landmarks, as well as 3DCRT plans treating the RTOG consensus volume. The patients were all T3, were node-negative (N = 1) or node-positive (N = 9), and were planned to a total dose of 45-Gy. Pairwise comparisons were made between IMRT and 3DCRT plans with respect to dose-volume histogram parameters. IMRT plans had superior PTV coverage, dose homogeneity, and conformality in treatment of the gross disease and at-risk nodal volume, in comparison to 3DCRT. Additionally, in comparison to the 3DCRT plans, IMRT achieved a concomitant reduction in doses to the bowel (small bowel mean dose: 18.6-Gy IMRT versus 25.2-Gy 3DCRT; p = 0.005), bladder (V40Gy: 56.8% IMRT versus 75.4% 3DCRT; p = 0.005), pelvic bones (V40Gy: 47.0% IMRT versus 56.9% 3DCRT; p = 0.005), and femoral heads (V40Gy: 3.4% IMRT versus 9.1% 3DCRT; p = 0.005), with an improvement in absolute volumes of small bowel receiving dose levels known to induce clinically-relevant acute toxicity (small bowel V15Gy: 138-cc IMRT versus 157-cc 3DCRT; p = 0.005). We found that the IMRT treatment volumes were typically larger than that covered by classic bony landmark-derived fields, without incurring penalty with respect to adjacent organs-at-risk. For rectal carcinoma, IMRT, compared to 3DCRT, yielded plans superior with respect to target coverage, homogeneity, and conformality, while lowering dose to adjacent organs-at-risk. This is achieved despite treating larger volumes, raising the possibility of a clinically-relevant improvement in the therapeutic ratio through the use of IMRT with a belly-board apparatus.