Zhu Jian, Simon Antoine, Haigron Pascal, Lafond Caroline, Acosta Oscar, Shu Huazhong, Castelli Joel, Li Baosheng, De Crevoisier Renaud
Laboratory of Image Science and Technology, Southeast University, Nanjing, Jiangsu; Department of Radiation Oncology, Shandong Cancer Hospital & Institute, Jinan; Centre de Recherche en Information Biomédicale Sino-français, Nanjing, People's Republic of China.
Centre de Recherche en Information Biomédicale Sino-français, Nanjing, People's Republic of China; Institut National de la Sante et de la Recherche Medicale, U1099; Laboratory of Signal and Image Processing (LTSI), University of Rennes 1.
Onco Targets Ther. 2016 Dec 12;9:7537-7544. doi: 10.2147/OTT.S116508. eCollection 2016.
To assess the benefits of bladder wall sub-volume equivalent uniform dose (EUD) constraints in prostate cancer intensity-modulated radiotherapy (IMRT) planning.
Two IMRT plans, with and without EUD constraints on the bladder wall, were generated using beams that deliver 80 Gy to the prostate and 46 Gy to the seminal vesicles and were compared in 53 prostate cancer patients. The bladder wall was defined as the volume between the external manually delineated wall and a contraction of 7 mm apart from it. The bladder wall was then separated into two parts: the internal-bladder wall (bla-in) represented by the portion of the bladder wall that intersected with the planning target volume (PTV) plus 5 mm extension; the external-bladder wall (bla-ex) represented by the remaining part of the bladder wall. In the IMRT plan with EUD constraints, the values of "" parameter for the EUD models were 10.0 for bla-in and 2.3 for bla-ex. The plans with and without EUD constraints were compared in terms of dose-volume histograms, 5-year bladder and rectum normal tissue complication probability values, as well as tumor control probability (TCP) values.
The use of bladder sub-volume EUD constraints decreased both the doses to the bladder wall (: 22.76% vs 19.65%, : 39.82 Gy vs 35.45 Gy) and the 5-year bladder complication probabilities (≥LENT/SOMA Grade 2: 20.35% vs 17.96%; bladder bleeding: 10.63% vs 8.64%). The doses to the rectum wall and the rectum complication probabilities were also slightly decreased by the EUD constraints compared to physical constraints only. The minimal dose and the of PTV were, however, slightly decreased by EUD optimization, nevertheless without significant difference in TCP values between the two plans, and the PTV parameters finally respected the Groupe d'Etude des Tumeurs Uro-Génitales recommendations.
Separating the bladder wall into two parts with appropriate EUD optimization may reduce bladder toxicity in prostate IMRT. Combining biological constraints with physical constraints in the organs at risk at the inverse planning step of IMRT may improve the dose distribution.
评估在前列腺癌调强放射治疗（IMRT）计划中膀胱壁亚体积等效均匀剂量（EUD）约束的益处。
为53例前列腺癌患者生成了两个IMRT计划，一个对膀胱壁有EUD约束，另一个没有，使用的射束给予前列腺80 Gy剂量，给予精囊46 Gy剂量，并对这两个计划进行比较。膀胱壁定义为手动勾勒的外部壁与距其7 mm收缩处之间的体积。然后将膀胱壁分为两部分：内部膀胱壁（bla-in）由与计划靶体积（PTV）相交的膀胱壁部分加5 mm延伸部分表示；外部膀胱壁（bla-ex）由膀胱壁的其余部分表示。在有EUD约束的IMRT计划中，EUD模型的“”参数值对于bla-in为10.0，对于bla-ex为2.3。从剂量体积直方图、5年膀胱和直肠正常组织并发症概率值以及肿瘤控制概率（TCP）值方面对有和没有EUD约束的计划进行比较。
使用膀胱亚体积EUD约束降低了膀胱壁的剂量（：22.76%对19.65%，：39.82 Gy对35.45 Gy）以及5年膀胱并发症概率（≥LENT/SOMA 2级：20.35%对17.96%；膀胱出血：10.63%对8.64%）。与仅采用物理约束相比，EUD约束也使直肠壁剂量和直肠并发症概率略有降低。然而，EUD优化使PTV的最小剂量和有所降低，但两个计划的TCP值无显著差异，并且PTV参数最终符合泌尿生殖系统肿瘤研究组的建议。
通过适当的EUD优化将膀胱壁分为两部分可降低前列腺IMRT中的膀胱毒性。在IMRT逆向计划步骤中，将生物约束与危险器官的物理约束相结合可能会改善剂量分布。
