Radiation Therapy Program, British Columbia Cancer Agency-Vancouver Island Centre, Victoria, British Columbia, Canada.
Int J Radiat Oncol Biol Phys. 2010 Jan 1;76(1):287-95. doi: 10.1016/j.ijrobp.2009.05.038.
Volumetric modulated arc therapy (VMAT) is a novel extension of conventional intensity-modulated radiotherapy (cIMRT), in which an optimized three-dimensional dose distribution may be delivered in a single gantry rotation. VMAT is the predecessor to RapidArc (Varian Medical System). This study compared VMAT with cIMRT and with conventional modified wide-tangent (MWT) techniques for locoregional radiotherapy for left-sided breast cancer, including internal mammary nodes.
Therapy for 5 patients previously treated with 50 Gy/25 fractions using nine-field cIMRT was replanned with VMAT and MWT. Comparative endpoints were planning target volume (PTV) dose homogeneity, doses to surrounding structures, number of monitor units, and treatment delivery time.
For VMAT, two 190 degrees arcs with 2-cm overlapping jaws were required to optimize over the large treatment volumes. Treatment plans generated using VMAT optimization resulted in PTV homogeneity similar to that of cIMRT and MWT. The average heart volumes receiving >30 Gy for VMAT, cIMRT, and MWT were 2.6% +/- 0.7%, 3.5% +/- 0.8%, and 16.4% +/- 4.3%, respectively, and the average ipsilateral lung volumes receiving >20 Gy were 16.9% +/- 1.1%, 17.3% +/- 0.9%, and 37.3% +/- 7.2%, respectively. The average mean dose to the contralateral medial breast was 3.2 +/- 0.6 Gy for VMAT, 4.3 +/- 0.4 Gy for cIMRT, and 4.4 +/- 4.7 Gy for MWT. The healthy tissue volume percentages receiving 5 Gy were significantly larger with VMAT (33.1% +/- 2.1%) and IMRT (45.3% +/- 3.1%) than with MWT (19.4% +/- 3.7%). VMAT reduced the number of monitor units by 30% and the treatment time by 55% compared with cIMRT.
VMAT achieved similar PTV coverage and sparing of organs at risk, with fewer monitor units and shorter delivery time than cIMRT.
容积调强弧形治疗（VMAT）是常规调强放疗（cIMRT）的一种新扩展，它可以在单个机架旋转中提供优化的三维剂量分布。VMAT 是 RapidArc（瓦里安医疗系统）的前身。本研究比较了 VMAT 与 cIMRT 和传统的改良宽切线（MWT）技术在左侧乳腺癌的局部区域放疗中的应用，包括内乳淋巴结。
对 5 例先前接受 50 Gy/25 次分割的 9 野 cIMRT 治疗的患者进行了 VMAT 和 MWT 再计划。比较的终点是计划靶区（PTV）剂量均匀性、周围结构剂量、监测器单位数量和治疗输送时间。
对于 VMAT，需要两个 190 度的弧形，带有 2 厘米的重叠钳口，以优化大的治疗体积。使用 VMAT 优化生成的治疗计划导致 PTV 均匀性与 cIMRT 和 MWT 相似。VMAT、cIMRT 和 MWT 的平均心脏体积接受 >30 Gy 的比例分别为 2.6% +/- 0.7%、3.5% +/- 0.8%和 16.4% +/- 4.3%，同侧肺接受 >20 Gy 的平均体积分别为 16.9% +/- 1.1%、17.3% +/- 0.9%和 37.3% +/- 7.2%。对侧内侧乳房的平均平均剂量分别为 VMAT 3.2 +/- 0.6 Gy、cIMRT 4.3 +/- 0.4 Gy 和 MWT 4.4 +/- 4.7 Gy。VMAT 的健康组织体积百分比为 33.1% +/- 2.1%，IMRT 为 45.3% +/- 3.1%，均明显大于 MWT 的 19.4% +/- 3.7%。与 cIMRT 相比，VMAT 减少了 30%的监测器单位和 55%的治疗时间。
VMAT 达到了与 cIMRT 相似的 PTV 覆盖率和危及器官的保护，同时减少了监测器单位数量和缩短了治疗时间。
