Sanford Lana, Molloy Janelle, Kumar Sameera, Randall Marcus, McGarry Ronald, Pokhrel Damodar
Department of Radiation Medicine, University of Kentucky, Lexington, KY, USA.
J Appl Clin Med Phys. 2019 Jan;20(1):118-127. doi: 10.1002/acm2.12500. Epub 2018 Dec 8.
PURPOSE/OBJECTIVES: To evaluate the plan quality and treatment delivery efficiency of single-isocenter/two-lesions volumetric modulated arc therapy (VMAT) lung stereotactic body radiation therapy (SBRT).
MATERIALS/METHODS: Eight consecutive patients with two peripherally located early stage nonsmall-cell-lung cancer (NSCLC) lung lesions underwent single-isocenter highly conformal noncoplanar VMAT SBRT treatment in our institution. A single-isocenter was placed between the two lesions. Doses were 54 or 50 Gy in 3 and 5 fractions respectively. Patients were treated every other day. Plans were calculated in Eclipse with AcurosXB algorithm and normalized to at least 95% of the planning target volume (PTV) receiving 100% of the prescribed dose. For comparison, two-isocenter plans (isocenter placed centrally in each target) were retrospectively created. Conformity indices (CIs), heterogeneity index (HI), gradient index (GI), gradient distance (GD), and D were calculated. The normal lung V5, V10, V20, mean lung dose (MLD) and other organs at risk (OARs) doses were evaluated. Total number of monitor units (MUs), beam-on time, and patient-specific quality assurance (QA) results were recorded.
The mean isocenter to tumor distance was 6.7 ± 2.3 cm. The mean combined PTV was 44.0 ± 23.4 cc. There was no clinically significant difference in CI, HI, GD, GI, D , and V20 including most of the OARs between single-isocenter and two-isocenter lung SBRT plans, evaluated per RTOG guidelines. However, for single-isocenter plans as the distance between the lesions increased, the V5, V10, and MLD increased, marginally. The total number of MUs and beam-on time was reduced by a factor of 1.5 for a single-isocenter plan compared to a two-isocenter plan. The single-isocenter/two-lesions VMAT lung SBRT QA plans demonstrated an accurate dose delivery of 98.1 ± 3.2% for clinical gamma passing rate of 3%/3 mm.
The SBRT treatment of two peripherally located lung lesions with a centrally placed single-isocenter was dosimetrically equivalent to two-isocenter plans. Faster treatment delivery for single-isocenter treatment can improve patient compliance and reduce the amount of intrafraction motion errors for well-suited patients.
目的/目标：评估单等中心/双病灶容积调强弧形放疗（VMAT）肺立体定向体部放疗（SBRT）的计划质量和治疗实施效率。
材料/方法：8例连续的患有两个外周型早期非小细胞肺癌（NSCLC）肺部病灶的患者在我院接受了单等中心高剂量适形非共面VMAT SBRT治疗。在两个病灶之间设置一个单等中心。剂量分别为54 Gy分3次或50 Gy分5次。患者每隔一天接受一次治疗。在Eclipse中使用AcurosXB算法计算计划，并归一化至至少95%的计划靶体积（PTV）接受100%的处方剂量。为作比较，回顾性创建了双等中心计划（等中心置于每个靶区中心）。计算了适形指数（CI）、不均匀性指数（HI）、梯度指数（GI）、梯度距离（GD）和D。评估了正常肺组织的V5、V10、V20、平均肺剂量（MLD）以及其他危及器官（OARs）的剂量。记录了监测单位（MUs）总数、照射时间以及患者特异性质量保证（QA）结果。
等中心至肿瘤的平均距离为6.7±2.3 cm。联合PTV的平均体积为44.0±23.4 cc。根据美国放射肿瘤学会（RTOG）指南评估，单等中心和双等中心肺SBRT计划在CI、HI、GD、GI、D以及包括大多数OARs在内的V20方面无临床显著差异。然而，对于单等中心计划，随着病灶间距离增加，V5、V10和MLD略有增加。与双等中心计划相比，单等中心计划的MUs总数和照射时间减少了1.5倍。单等中心/双病灶VMAT肺SBRT QA计划临床剂量通过率为3%/3 mm时，剂量输送的准确性为98.1±3.2%。
采用置于中心的单等中心对两个外周型肺部病灶进行SBRT治疗，在剂量学上等同于双等中心计划。单等中心治疗更快的治疗实施速度可提高患者依从性，并减少适合患者的分次内运动误差量。
