Chung Heeteak, Polf Jerimy, Badiyan Shahed, Biagioli Matthew, Fernandez Daniel, Latifi Kujtim, Wilder Richard, Mehta Minesh, Chuong Michael
Department of Radiation Oncology, University of Maryland, Baltimore School of Medicine, Baltimore, MD, USA.
Department of Radiation Oncology, Florida Hospital Cancer Institute, Orlando, FL, USA.
J Appl Clin Med Phys. 2017 Jan;18(1):32-39. doi: 10.1002/acm2.12001. Epub 2016 Nov 21.
The purpose of this study was to evaluate whether a spacer inserted in the prerectal space could reduce modeled rectal dose and toxicity rates for patients with prostate cancer treated in silico with pencil beam scanning (PBS) proton therapy. A total of 20 patients were included in this study who received photon therapy (12 with rectal spacer (DuraSeal™ gel) and 8 without). Two PBS treatment plans were retrospectively created for each patient using the following beam arrangements: (1) lateral-opposed (LAT) fields and (2) left and right anterior oblique (LAO/RAO) fields. Dose volume histograms (DVH) were generated for the prostate, rectum, bladder, and right and left femoral heads. The normal tissue complication probability (NTCP) for ≥grade 2 rectal toxicity was calculated using the Lyman-Kutcher-Burman model and compared between patients with and without the rectal spacer. A significantly lower mean rectal DVH was achieved in patients with rectal spacer compared to those without. For LAT plans, the mean rectal V70 with and without rectal spacer was 4.19 and 13.5%, respectively. For LAO/RAO plans, the mean rectal V70 with and without rectal spacer was 5.07 and 13.5%, respectively. No significant differences were found in any rectal dosimetric parameters between the LAT and the LAO/RAO plans generated with the rectal spacers. We found that ≥ 9 mm space resulted in a significant decrease in NTCP modeled for ≥grade 2 rectal toxicity. Rectal spacers can significantly decrease modeled rectal dose and predicted ≥grade 2 rectal toxicity in prostate cancer patients treated in silico with PBS. A minimum of 9 mm separation between the prostate and anterior rectal wall yields the largest benefit.
本研究的目的是评估在直肠前间隙插入一个间隔物是否可以降低在计算机模拟中接受笔形束扫描（PBS）质子治疗的前列腺癌患者的模拟直肠剂量和毒性发生率。本研究共纳入20例接受光子治疗的患者（12例使用直肠间隔物（DuraSeal™凝胶），8例未使用）。使用以下射野布置为每位患者回顾性创建两个PBS治疗计划：（1）对侧野（LAT）和（2）左右前斜野（LAO/RAO）。生成前列腺、直肠、膀胱以及左右股骨头的剂量体积直方图（DVH）。使用Lyman-Kutcher-Burman模型计算≥2级直肠毒性的正常组织并发症概率（NTCP），并在有和没有直肠间隔物的患者之间进行比较。与没有直肠间隔物的患者相比，有直肠间隔物的患者平均直肠DVH显著更低。对于LAT计划，有和没有直肠间隔物时直肠的平均V70分别为4.19%和13.5%。对于LAO/RAO计划，有和没有直肠间隔物时直肠的平均V70分别为5.07%和13.5%。在使用直肠间隔物生成的LAT和LAO/RAO计划之间，任何直肠剂量学参数均未发现显著差异。我们发现≥9mm的间隙可使模拟的≥2级直肠毒性的NTCP显著降低。直肠间隔物可显著降低在计算机模拟中接受PBS治疗的前列腺癌患者的模拟直肠剂量和预测的≥2级直肠毒性。前列腺与直肠前壁之间至少9mm的间距可带来最大益处。
