Inokuchi Haruo, Mizowaki Takashi, Norihisa Yoshiki, Takayama Kenji, Ikeda Itaru, Nakamura Kiyonao, Nakamura Mitsuhiro, Hiraoka Masahiro
Department of Radiation Oncology and Image-Applied Therapy, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto, 606-8507, Japan.
Int J Clin Oncol. 2016 Feb;21(1):156-61. doi: 10.1007/s10147-015-0873-9. Epub 2015 Jul 12.
Several studies have confirmed a dosimetric advantage associated with use of a smaller leaf in intensity-modulated radiation therapy (IMRT). However, no studies have identified any clinical benefits. We investigated the effect of a smaller multileaf collimator (MLC) width on the onset of late rectal bleeding after high-dose prostate IMRT.
Two hundred and five prostate cancer patients were treated with a total dose of 78 Gy in 39 fractions by use of a dynamic MLC technique; however, two different MLC were used: a 10-mm-wide device and a 5-mm-wide device. Gastrointestinal toxicity and several clinical factors were assessed.
The 5-year actuarial risk of grade 2 or higher rectal bleeding was 6.9 % for the 10-mm-wide group (n = 132) and 1.8 % for the 5-mm-wide group (n = 73) (p = 0.04). The median estimated rectal doses for the two groups were 55.1 and 50.6 Gy (p < 0.001), respectively. Univariate analysis showed that acute toxicity, rectal V30-60, median rectal dose, normal tissue complication probability (NTCP), and MLC type were significant predictive factors for late rectal toxicity. In multivariate analysis, acute toxicity and NTCP remained significant.
In our planning approach for prostate IMRT, a decrease in MLC width from 10 to 5 mm contributed to further rectal dose reduction, which was the most important predictor of late rectal toxicity.
多项研究已证实，在调强放射治疗（IMRT）中使用较小的叶片具有剂量学优势。然而，尚无研究发现任何临床益处。我们研究了较小的多叶准直器（MLC）宽度对高剂量前列腺IMRT后晚期直肠出血发生的影响。
205例前列腺癌患者采用动态MLC技术，分39次给予总剂量78 Gy的治疗；然而，使用了两种不同的MLC：一种宽度为10 mm的装置和一种宽度为5 mm的装置。评估了胃肠道毒性和几个临床因素。
10 mm宽组（n = 132）2级或更高等级直肠出血的5年精算风险为6.9%，5 mm宽组（n = 73）为1.8%（p = 0.04）。两组的直肠中位估计剂量分别为55.1 Gy和50.6 Gy（p < 0.001）。单因素分析显示，急性毒性、直肠V30 - 60、直肠中位剂量、正常组织并发症概率（NTCP）和MLC类型是晚期直肠毒性的重要预测因素。多因素分析中，急性毒性和NTCP仍然具有显著性。
在我们的前列腺IMRT计划方法中，MLC宽度从10 mm减小到5 mm有助于进一步降低直肠剂量，这是晚期直肠毒性的最重要预测因素。
