Department of Radiation Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, 270 Dong An Road, Shanghai 200032, China.
Swedish Cancer Institute, 747 Broadway, Seattle, USA.
Radiol Oncol. 2015 Mar 3;49(1):91-8. doi: 10.2478/raon-2014-0033. eCollection 2015 Mar.
The aim of the study was to evaluate the dosimetric benefit of applying volumetric modulated arc therapy (VMAT) on the post-mastectomy left-sided breast cancer patients, with the involvement of internal mammary nodes (IMN).
The prescription dose was 50 Gy delivered in 25 fractions, and the clinical target volume included the left chest wall (CW) and IMN. VMAT plans were created and compared with intensity-modulated radiotherapy (IMRT) plans on Pinnacle treatment planning system. Comparative endpoints were dose homogeneity within planning target volume (PTV), target dose coverage, doses to the critical structures including heart, lungs and the contralateral breast, number of monitor units and treatment delivery time.
VMAT and IMRT plans showed similar PTV dose homogeneity, but, VMAT provided a better dose coverage for IMN than IMRT (p = 0.017). The mean dose (Gy), V30 (%) and V10 (%) for the heart were 13.5 ± 5.0 Gy, 9.9% ± 5.9% and 50.2% ± 29.0% by VMAT, and 14.0 ± 5.4 Gy, 10.6% ± 5.8% and 55.7% ± 29.6% by IMRT, respectively. The left lung mean dose (Gy), V20 (%), V10 (%) and the right lung V5 (%) were significantly reduced from 14.1 ± 2.3 Gy, 24.2% ± 5.9%, 42.4% ± 11.9% and 41.2% ± 12.3% with IMRT to 12.8 ± 1.9 Gy, 21.0% ± 3.8%, 37.1% ± 8.4% and 32.1% ± 18.2% with VMAT, respectively. The mean dose to the contralateral breast was 1.7 ± 1.2 Gy with VMAT and 2.3 ± 1.6 Gy with IMRT. Finally, VMAT reduced the number of monitor units by 24% and the treatment time by 53%, as compared to IMRT.
Compared to 5-be am step-and-shot IMRT, VMAT achieves similar or superior target coverage and a better normal tissue sparing, with fewer monitor units and shorter delivery time.
本研究旨在评估容积调强弧形治疗（VMAT）在涉及内乳淋巴结（IMN）的左侧乳腺癌根治术后患者中的剂量学优势。
处方剂量为 50 Gy，分 25 次给予，临床靶区包括左胸壁（CW）和 IMN。在 Pinnacle 治疗计划系统上创建 VMAT 计划，并与调强放疗（IMRT）计划进行比较。比较终点包括计划靶区（PTV）内的剂量均匀性、靶区剂量覆盖、包括心脏、肺和对侧乳房在内的关键结构的剂量、监测器单位数和治疗时间。
VMAT 和 IMRT 计划显示出相似的 PTV 剂量均匀性，但 VMAT 对 IMN 的剂量覆盖优于 IMRT（p = 0.017）。VMAT 组心脏的平均剂量（Gy）、V30（%）和 V10（%）分别为 13.5 ± 5.0 Gy、9.9% ± 5.9%和 50.2% ± 29.0%，IMRT 组分别为 14.0 ± 5.4 Gy、10.6% ± 5.8%和 55.7% ± 29.6%。左肺平均剂量（Gy）、V20（%）、V10（%）和右肺 V5（%）分别从 IMRT 的 14.1 ± 2.3 Gy、24.2% ± 5.9%、42.4% ± 11.9%和 41.2% ± 12.3%显著降低至 VMAT 的 12.8 ± 1.9 Gy、21.0% ± 3.8%、37.1% ± 8.4%和 32.1% ± 18.2%。VMAT 组对侧乳房的平均剂量为 1.7 ± 1.2 Gy，IMRT 组为 2.3 ± 1.6 Gy。与 IMRT 相比，VMAT 减少了 24%的监测器单位数和 53%的治疗时间。
与 5 野步进式 IMRT 相比，VMAT 可实现相似或更好的靶区覆盖和更好的正常组织保护，同时减少监测器单位数和缩短治疗时间。
