Tuomikoski Laura, Valli Aino, Tenhunen Mikko, Muren Ludvig, Vestergaard Anne
HUCH Cancer Center, Department of Oncology, Helsinki University Central Hospital, Finland.
HUCH Cancer Center, Department of Oncology, Helsinki University Central Hospital, Finland.
Radiother Oncol. 2015 Dec;117(3):448-52. doi: 10.1016/j.radonc.2015.10.012. Epub 2015 Nov 11.
The predominant approach to clinically applied adaptive radiotherapy (ART) for bladder cancer is daily selection of treatment plans from a plan library. In this study we have compared two clinical strategies for creating multiple planning target volumes (PTV) for ART of bladder cancer.
Online ART delivering 60 Gy in 30 fractions to the whole bladder was simulated for ten patients using two methods of creating plan libraries. In the RepeatCT method four planning CT scans were acquired at 15-min intervals, generating four CTVs with different bladder volumes. In the RepeatCBCT method one planning CT and four daily cone-beam CT images were combined using Boolean operators to form three composite CTVs. Plan selection rates and PTV volumes were evaluated, with the selected volumes averaged across 30 treatment fractions (PTV(mean)).
The PTV(mean) volume was on average 80 cm(3) smaller (p<0.001) in the RepeatCT method than in the RepeatCBCT method. Compared to the non-adaptive treatment, the PTV(mean) was reduced by 46% (range 33-53%, RepeatCT) and 36% (range 27-44%, RepeatCBCT).
Both methods reduced the PTV(mean) volume compared to the non-adaptive approach, but the reduction was larger using the strategy with repeat planning CT imaging. However, the strategy with combined CT and repeat CBCT imaging produced a more adequate range of PTV volumes.
膀胱癌临床应用自适应放疗（ART）的主要方法是每天从计划库中选择治疗计划。在本研究中，我们比较了两种为膀胱癌ART创建多个计划靶区（PTV）的临床策略。
使用两种创建计划库的方法，对10例患者模拟在线ART，将60 Gy分30次照射至整个膀胱。在重复CT方法中，每隔15分钟采集4次计划CT扫描，生成4个具有不同膀胱体积的临床靶区（CTV）。在重复锥形束CT（RepeatCBCT）方法中，使用布尔运算符将1次计划CT和4次每日锥形束CT图像组合，形成3个复合CTV。评估计划选择率和PTV体积，将选定体积在30个治疗分次中进行平均（PTV（均值））。
重复CT方法的PTV（均值）体积平均比重复CBCT方法小80 cm³（p < 0.001）。与非自适应治疗相比，PTV（均值）减少了46%（范围33 - 53%，重复CT）和36%（范围27 - 44%，重复CBCT）。
与非自适应方法相比，两种方法均降低了PTV（均值）体积，但采用重复计划CT成像策略时体积减小幅度更大。然而，联合CT和重复CBCT成像策略产生的PTV体积范围更合适。
