ATreP - Agenzia Provinciale per la Protonterapia, Via F.lli Perini, 181, 38122, Trento, Italy.
Strahlenther Onkol. 2012 Mar;188(3):216-25. doi: 10.1007/s00066-011-0038-3. Epub 2012 Feb 10.
Intensity-modulated radiation therapy (IMRT) is the state-of-the-art treatment for patients with malignant pleural mesothelioma (MPM). The goal of this work was to assess whether intensity-modulated proton therapy (IMPT) could further improve the dosimetric results allowed by IMRT.
We re-planned 7 MPM cases using both photons and protons, by carrying out IMRT and IMPT plans. For both techniques, conventional dose comparisons and normal tissue complication probability (NTCP) analysis were performed. In 3 cases, additional IMPT plans were generated with different beam dimensions.
IMPT allowed a slight improvement in target coverage and clear advantages in dose conformity (p < 0.001) and dose homogeneity (p = 0.01). Better organ at risk (OAR) sparing was obtained with IMPT, in particular for the liver (D(mean) reduction of 9.5 Gy, p = 0.001) and ipsilateral kidney (V(20) reduction of 58%, p = 0.001), together with a very large reduction of mean dose for the contralateral lung (0.2 Gy vs 6.1 Gy, p = 0.0001). NTCP values for the liver showed a systematic superiority of IMPT with respect to IMRT for both the esophagus (average NTCP 14% vs. 30.5%) and the ipsilateral kidney (p = 0.001). Concerning plans obtained with different spot dimensions, a slight loss of target coverage was observed along with sigma increase, while maintaining OAR irradiation always under planning constraints.
Results suggest that IMPT allows better OAR sparing with respect to IMRT, mainly for the liver, ipsilateral kidney, and contralateral lung. The use of a spot dimension larger than 3 × 3 mm (up to 9 × 9 mm) does not compromise dosimetric results and allows a shorter delivery time.
调强适形放疗（IMRT）是恶性胸膜间皮瘤（MPM）患者的一种先进治疗方法。本研究旨在评估强度调制质子治疗（IMPT）是否可以进一步改善 IMRT 允许的剂量学结果。
我们对 7 例 MPM 患者分别进行了光子和质子的再计划，包括 IMRT 和 IMPT 计划。对于两种技术，均进行了常规剂量比较和正常组织并发症概率（NTCP）分析。在 3 例患者中，使用不同的射束尺寸生成了额外的 IMPT 计划。
IMPT 略微改善了靶区覆盖，在剂量适形性（p<0.001）和剂量均匀性（p=0.01）方面具有明显优势。与 IMRT 相比，IMPT 获得了更好的危及器官（OAR）保护，特别是对于肝脏（Dmean 降低 9.5Gy，p=0.001）和同侧肾脏（V20 降低 58%，p=0.001），同时对对侧肺的平均剂量也有很大降低（0.2Gy 与 6.1Gy，p=0.0001）。对于食管（平均 NTCP 为 14%与 30.5%，p=0.001）和同侧肾脏（p=0.001），肝脏的 NTCP 值显示 IMPT 相对于 IMRT 具有系统优势。对于不同光斑尺寸获得的计划，观察到靶区覆盖略有损失，同时 sigma 增加，而始终保持 OAR 照射在计划限制内。
结果表明，与 IMRT 相比，IMPT 可以更好地保护 OAR，主要是肝脏、同侧肾脏和对侧肺。使用大于 3×3mm（最大可达 9×9mm）的光斑尺寸不会影响剂量学结果，并可以缩短治疗时间。
