Department of Radiation Oncology, Zurich University Hospital, Switzerland.
Int J Radiat Oncol Biol Phys. 2010 Oct 1;78(2):628-34. doi: 10.1016/j.ijrobp.2009.11.006. Epub 2010 Apr 10.
To perform comparative planning for intensity-modulated radiotherapy (IMRT) and proton therapy (PT) for malignant pleural mesothelioma after radical surgery.
Eight patients treated with IMRT after extrapleural pleuropneumonectomy (EPP) were replanned for PT, comparing dose homogeneity, target volume coverage, and mean and maximal dose to organs at risk. Feasibility of PT was evaluated regarding the dose distribution with respect to air cavities after EPP.
Dose coverage and dose homogeneity of the planning target volume (PTV) were significantly better for PT than for IMRT regarding the volume covered by >95% (V95) for the high-dose PTV. The mean dose to the contralateral kidney, ipsilateral kidney, contralateral lung, liver, and heart and spinal cord dose were significantly reduced with PT compared with IMRT. After EPP, air cavities were common (range, 0-850 cm(3)), decreasing from 0 to 18.5 cm(3)/day. In 2 patients, air cavity changes during RT decreased the generalized equivalent uniform dose (gEUD) in the case of using an a value of < - 10 to the PTV2 to <2 Gy in the presence of changing cavities for PT, and to 40 Gy for IMRT. Small changes were observed for gEUD of PTV1 because PTV1 was reached by the beams before air.
Both PT and IMRT achieved good target coverage and dose homogeneity. Proton therapy accomplished additional dose sparing of most organs at risk compared with IMRT. Proton therapy dose distributions were more susceptible to changing air cavities, emphasizing the need for adaptive RT and replanning.
为根治性手术后恶性胸膜间皮瘤行调强放疗（IMRT）和质子治疗（PT）进行对比规划。
对 8 例行胸膜外全肺切除术（EPP）后行 IMRT 的患者进行 PT 再规划，比较剂量均匀性、靶区覆盖、危及器官的平均剂量和最大剂量。根据 EPP 后空气腔的剂量分布评估 PT 的可行性。
PT 覆盖高剂量 PTV 的 V95 体积比 IMRT 显著更好，PT 规划靶区（PTV）的剂量覆盖和均匀性明显更好。与 IMRT 相比，PT 可显著降低对侧肾脏、同侧肾脏、对侧肺、肝脏、心脏和脊髓剂量的平均剂量。EPP 后，空气腔很常见（范围 0-850cm3），每天减少 0-18.5cm3。在 2 例患者中，由于空气腔变化，在使用 < - 10 的 a 值时，PT 中 PTV2 的广义等效均匀剂量（gEUD）降至 <2Gy，而 IMRT 则降至 40Gy。由于空气腔的存在，PTV1 中 gEUD 变化较小，因为光束先到达 PTV1 再到达空气腔。
PT 和 IMRT 均能达到良好的靶区覆盖和剂量均匀性。与 IMRT 相比，质子治疗能进一步保护大多数危及器官的剂量。质子治疗剂量分布更容易受到空气腔变化的影响，这强调了自适应放疗和重新规划的必要性。
