日本京都大学前列腺癌三个外放疗计划比较

Comparison of Three Radiotherapy Treatment Planning Protocols of Definitive External-beam Radiation for Localized Prostate Cancer at Kyoto University

[目的]比较分析日本京都大学医院对局限性前列腺癌实施治疗的三个外放疗计划。[方法]从放疗计划数据库中调取5例局限性前列腺癌的定位CT影像资料,分别按先前的三维适形计划(old 3DCRT)、新的3DCRT(new 3DCRT)和调强放疗计划(IMRT)做计划,根据剂量体积直方图比较各计划剂量分布的差异。[结果]临床靶区(CTV,即前列腺)的剂量覆盖在三个计划中都基本相似并达到理想的剂量分布,但对于计划靶区(PTV),V95、D95和适形指数值在IMRT分别为99%、97%和0.88;在new 3DCRT为93.9%、94.5%和0.76;在old 3DCRT为59.6%、82.9%和0.6。在IMRT计划中PTV的剂量不均整值较new 3DCRT计划中的高;直肠壁接受大于40Gy剂量的体积百分数在IMRT和new 3DCRT中差异不大,在old 3DCRT中最低。[结论]局限性前列腺癌动态弧三维适形放疗计划可以实现和调强放疗计划相比拟的靶区覆盖及对直肠壁的保护,尽管调强放疗计划可以达到更适形的靶区剂量分布,但代价是更高的剂量不均整。先前的三维适形计划达不到目前对PTV靶区的充分覆盖。

[Purpose] Three radiotherapy treatment planning （RTTP） protocols with external-beam radiation for localized prostate cancer at Kyoto University were compared. [Methods] Treatment plans were created according to three different RTTP protocols old 3DCRT, new 3DCRT and IMRT protocol from CT data of five patients with localized prostate cancer. Differences in dose distribution were evaluated and compared based on dose-volume histogram （DVH） analyses. [Results] The coverage of the clinical target volume （CTV, prostate alone） was comparable among the three RTTP protocols. However, the averaged V95, D95, and conformity index of the planning target volume （PTV） were 99%, 97% and 0.88 with the IMRT; 93.9%, 94.5% and 0.76 with the new 3DCRT; and 59.6%, 82.9%, and 0.6 with the old 3D-CRT protocol, respectively. In homogeneity in doses to the PTV was higher in the IMRT protocol than that in the new 3DCRT protocol. Pecentage of volume in rectal wall received radiation dose〉40Gy was lowest in old 3DCRT protocol, with no significant difference between new 3DCRT and IMRT protocol. [Conclusion] The dynamic-arc 3DCRT and IMRT protocols are generally comparable in terms of both the PTV coverage and protection of rectal wall. Although the IMRT protocol has most conformal dose distribution to the PTV in return for higher but acceptable dose inhomogeneity. The old 3DCRT protocol could not achieve the goals for the PTV set in the new 3DCRT and IMRT protocols.