Proton Therapy Division, Shizuoka Cancer Center Research Institute, Nagaizumi, Shizuoka 411-8777, Japan.
J Radiat Res. 2012;53(2):272-80. doi: 10.1269/jrr.11136. Epub 2011 Dec 1.
Intensity-modulated proton therapy (IMPT) is expected to improve treatment results with fewer side effects than other proton therapies. The purpose of this study was to evaluate the tumor sites for which IMPT was effective under the same beam calculation conditions by planning IMPT for typical cases treated with passive scattering proton therapy (PSPT). We selected 16 cases of nasal cavity, lung, liver or prostate cancers as typical tumor sites receiving PSPT. The dose distributions and dose volume histograms optimized by the IMPT were compared with those optimized by the PSPT. We took particular note of the doses to the skin and organs at risk (OAR) when PSPT was replaced by IMPT. Furthermore, an improvement of the beam angles was also performed to obtain better dose distributions in the IMPT. The IMPT with the same beam angles resulted in near-maximum doses to the skin of average 78%, 64%, 84% and 99% of the PSPT doses for nasal cavity, lung, liver, and prostate cancers, respectively. However, it was difficult to improve the dose homogeneity of the target volume. The change of the IMPT beam angles could reduce the doses to OARs and skin in the case of the nasal cavity, while it had limited effect in the other cases. We concluded that IMPT was effective for reducing the doses to some OARs when treating nasal cavity, lung, liver and prostate cancers. The selection of beam angles was important in the IMPT optimization, especially for nasal cavity cancers.
调强质子治疗（IMPT）有望在减少副作用的情况下提高治疗效果，优于其他质子治疗。本研究旨在通过为接受被动散射质子治疗（PSPT）的典型病例规划 IMPT，评估在相同射束计算条件下 IMPT 有效的肿瘤部位。我们选择了 16 例鼻腔、肺、肝或前列腺癌作为接受 PSPT 治疗的典型肿瘤部位。比较了由 IMPT 优化的剂量分布和剂量体积直方图与由 PSPT 优化的剂量分布和剂量体积直方图。当 PSPT 被 IMPT 取代时，我们特别注意皮肤和危及器官（OAR）的剂量。此外，还进行了射束角度的改进，以在 IMPT 中获得更好的剂量分布。使用相同射束角度的 IMPT 导致鼻腔、肺、肝和前列腺癌的皮肤平均达到 78%、64%、84%和 99%的最大剂量，分别为 PSPT 剂量的近最大值。然而，很难改善靶区的剂量均匀性。改变 IMPT 射束角度可以减少鼻腔病例中 OAR 和皮肤的剂量，但在其他病例中效果有限。我们得出结论，在治疗鼻腔、肺、肝和前列腺癌时，IMPT 可有效降低某些 OAR 的剂量。在 IMPT 优化中，射束角度的选择很重要，特别是对于鼻腔癌。
