PeterMac Cancer Centre, East Melbourne, Australia.
Clin Oncol (R Coll Radiol). 2010 Apr;22(3):179-84. doi: 10.1016/j.clon.2010.01.004. Epub 2010 Feb 18.
Therapeutic radiotherapy to lesions of the skull base is limited by complex target shapes and their proximity to organs at risk. Intensity-modulated radiotherapy (IMRT) using helical tomotherapy may result in improved dose distributions and safer dose escalation. The aim of this study was to compare plan efficacy and efficiency using, linac-based micro-multileaf collimator (mMLC) IMRT and helical tomotherapy.
Five cases of skull base meningioma, previously treated with three-dimensional conformal radiotherapy (50 Gy/30 fractions) were identified. They were re-planned to a dose of 60 Gy/30 fractions using IMRT with Moduleaf mMLC (2.5 mm) and helical tomotherapy. Plan efficacy was compared using measures of PTV(60) coverage (D(min), D(max), V(90%), V(95%) and V(100%)). Plan efficiency was assessed by comparing estimated beam-on times.
The critical structure dose was limited to below predetermined tolerance levels in all cases, with similar doses obtained between techniques. The average PTV(60)D(max), D(min), D(med), D(mean), V(90%), V(95%) and V(100%) across the five cases achieved were as follows: mMLC IMRT: 64.9 Gy, 40.1 Gy, 60 Gy, 59.6 Gy, 95.4%, 88.8% and 69.2%, respectively; helical tomotherapy: 67.2 Gy, 50.3 Gy, 60 Gy, 59.9 Gy, 95.8%, 83.5% and 51.9%, respectively. The average treatment time per fraction was 18.4 min for IMRT with mMLC and 6.7 min for helical tomotherapy.
This study shows that safe dose escalation to a dose of 60G y to skull base lesions can be achieved; using either mMLC- or helical tomotherapy-based IMRT. A plan comparison between the two solutions is difficult, but they seem to be similar in efficacy with any small differences being difficult to interpret and of questionable clinical significance. Helical tomotherapy has the advantage of a significantly decreased beam-on time.
颅底病变的治疗性放射治疗受到复杂靶区形状和其与危及器官之间的接近程度的限制。采用螺旋断层放疗（Helical Tomotherapy）的调强放疗（Intensity-Modulated Radiotherapy，IMRT）可能会改善剂量分布并实现更安全的剂量提升。本研究的目的是比较使用基于直线加速器的微多叶准直器（Micro-Multileaf Collimator，mMLC）调强放疗和螺旋断层放疗的计划疗效和效率。
我们确定了 5 例颅底脑膜瘤患者，他们之前接受过三维适形放疗（三维适形放疗 50 Gy/30 次）。使用 2.5mm 的 mMLC 模块对这些患者重新进行 60 Gy/30 次的调强放疗计划。使用 PTV（60）覆盖率（Dmin、Dmax、V90%、V95%和 V100%）等指标比较计划疗效。通过比较预估射束开启时间评估计划效率。
在所有病例中，关键结构的剂量均限制在预定耐受水平以下，两种技术获得的剂量相似。5 例患者的平均 PTV（60）Dmax、Dmin、Dmed、Dmean、V90%、V95%和 V100%值如下：mMLC-IMRT：64.9 Gy、40.1 Gy、60 Gy、59.6 Gy、95.4%、88.8%和 69.2%；螺旋断层放疗：67.2 Gy、50.3 Gy、60 Gy、59.9 Gy、95.8%、83.5%和 51.9%。mMLC-IMRT 每分次的平均治疗时间为 18.4 分钟，而螺旋断层放疗为 6.7 分钟。
本研究表明，颅底病变的安全剂量提升至 60Gy 是可行的，可以使用 mMLC-或螺旋断层放疗的基于调强放疗的方案来实现。两种方案之间的计划比较较为困难，但它们在疗效上似乎相似，任何微小的差异都难以解释，且具有临床意义。螺旋断层放疗的优势在于射束开启时间显著缩短。
