Webster Gareth J, Rowbottom Carl G, Ho Kean F, Slevin Nick J, Mackay Ranald I
North Western Medical Physics, Christie Hospital National Health Service Foundation Trust, Manchester, UK.
Int J Radiat Oncol Biol Phys. 2008 Oct 1;72(2):617-22. doi: 10.1016/j.ijrobp.2008.06.1495.
Concern exists that widespread implementation of whole-field intensity-modulated radiotherapy (IMRT) for the treatment of head-and-neck cancer has resulted in increased levels of dysphagia relative to those seen with conventional planning. Other investigators have suggested an alternative junctioned-IMRT (J-IMRT) method, which matches an IMRT plan to a centrally blocked neck field to restrict the laryngeal dose and reduce dysphagia. The effect on target coverage and sparing of organs at risk, including laryngeal sparing, in the optimization was evaluated and compared with that achieved using a J-IMRT technique.
A total of 13 oropharyngeal cancer whole-field IMRT plans were planned with and without including laryngeal sparing in the optimization. A comparison of the target coverage and sparing of organs at risk was made using the resulting dose-volume histograms and dose distribution. The nine plans with disease located superior to the level of the larynx were replanned using a series of J-IMRT techniques to compare the two laryngeal-sparing techniques.
An average mean larynx dose of 29.1 Gy was achieved if disease did not extend to the level of the larynx, with 38.8 Gy for disease extending inferiorly and close to the larynx (reduced from 46.2 and 47.7 Gy, respectively, without laryngeal sparing). Additional laryngeal sparing could be achieved with J-IMRT (mean dose 24.4 Gy), although often at the expense of significantly reduced coverage of the target volume and with no improvement to other areas of the IMRT plan.
The benefits of J-IMRT can be achieved with whole-field IMRT if laryngeal sparing is incorporated into the class solution. Inclusion of laryngeal sparing had no effect on other parameters in the plan.
人们担心对头颈部癌广泛实施全野调强放射治疗（IMRT）导致吞咽困难水平相对于传统计划有所增加。其他研究者提出了一种替代的衔接式IMRT（J-IMRT）方法，即将IMRT计划与中央遮挡的颈部野匹配，以限制喉部剂量并减少吞咽困难。评估了优化过程中对靶区覆盖和危及器官的保护效果，包括对喉部的保护，并与使用J-IMRT技术所取得的效果进行比较。
总共制定了13个口咽癌全野IMRT计划，分别在优化过程中纳入和不纳入喉部保护。使用所得的剂量体积直方图和剂量分布对靶区覆盖和危及器官的保护进行比较。对9个病变位于喉水平以上的计划采用一系列J-IMRT技术重新规划，以比较两种喉部保护技术。
如果病变未延伸至喉水平，平均喉部平均剂量为29.1 Gy；病变向下延伸并靠近喉部时，平均喉部平均剂量为38.8 Gy（无喉部保护时分别为46.2 Gy和47.7 Gy）。J-IMRT可实现额外的喉部保护（平均剂量24.4 Gy），尽管这通常是以显著减少靶区体积覆盖为代价，且对IMRT计划的其他区域无改善。
如果在分级解决方案中纳入喉部保护，全野IMRT可实现J-IMRT的益处。纳入喉部保护对计划中的其他参数无影响。
