Doring C, Wang I, Podgorsak M
SUNY Buffalo and Roswell Park Cancer Institute, Buffalo, NY.
Med Phys. 2012 Jun;39(6Part20):3853. doi: 10.1118/1.4735728.
To demonstrate the dosimetric potential of volumetric modulated arc therapy (VMAT) for the treatment of patients with medically inoperable stage I/II non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT).
Fourteen patients treated with 3D-CRT with varying tumor locations, tumor sizes and dose fractionation schemes were chosen for study. The target prescription doses were 48 Gy in 4 fractions, 52.5 Gy in 5 fractions, 57.5 Gy in 5 fractions and 60 Gy in 3 fractions for 2, 5, 1 and 6 patients, respectively. VMAT treatment plans with a mix of 2-3 full and/or partial non-coplanar arcs with 5°-25° separations were retrospectively generated using Eclipse version 10.0. The 3D-CRT and VMAT plans were then evaluated by comparing their target dose, critical structure dose, high dose spillage, and low dose spillage as defined according to RTOG 0813 and RTOG 0236 protocols.
The VMAT treatment plans yielded an average 9.6-33.7% reduction in dose to critical structures and an average 12.0-12.5% increase in conformity compared with the treated 3D-CRT plans. The D2cm improved with VMAT in 11 of 14 cases. The 3 that worsened were still within the acceptance criteria. Of the 14 3D-CRT plans, 7 had a D2cm minor deviation, while only one of the 14 VMAT plans had a D2cm minor deviation. The R50% improved in 13 of the 14 VMAT cases. The 1 case that worsened was still within the acceptance criteria of the RTOG protocol. Of the 14 3D-CRT plans, 7 had an R50% deviation. Only 1 of the 14 VMAT plans had an R50% deviation, but it was still improved compared to the 3D-CRT plan.
In this cohort of patients, no dosimetric compromises resulted from planning SBRT treatments with VMAT relative to the 3D-CRT treatment plans actually used in their treatment.
证明容积调强弧形放疗（VMAT）联合立体定向体部放疗（SBRT）治疗医学上无法手术的Ⅰ/Ⅱ期非小细胞肺癌（NSCLC）患者的剂量学潜力。
选择14例接受三维适形放疗（3D-CRT）治疗的患者，其肿瘤位置、大小及剂量分割方案各异。2、5、1和6例患者的靶区处方剂量分别为48 Gy分4次、52.5 Gy分5次、57.5 Gy分5次和60 Gy分3次。使用Eclipse 10.0版本回顾性生成包含2-3个全弧和/或部分非共面弧且间隔为5°-25°的VMAT治疗计划。然后根据RTOG 0813和RTOG 0236方案，通过比较3D-CRT和VMAT计划的靶区剂量、关键结构剂量、高剂量溢出和低剂量溢出，对二者进行评估。
与实际治疗的3D-CRT计划相比，VMAT治疗计划使关键结构的剂量平均降低了9.6%-33.7%，适形度平均提高了12.0%-12.5%。14例患者中有11例的D2cm（距靶区2 cm处的剂量）在VMAT治疗后得到改善。恶化的3例仍在可接受标准范围内。在14个3D-CRT计划中，7个存在D2cm轻微偏差，而14个VMAT计划中只有1个存在D2cm轻微偏差。14例VMAT病例中有13例的R50%（50%等剂量线所包含的体积）得到改善。恶化的1例仍在RTOG方案的可接受标准范围内。在14个3D-CRT计划中，7个存在R50%偏差。14个VMAT计划中只有1个存在R50%偏差，但与3D-CRT计划相比仍有所改善。
在该队列患者中，相对于实际用于其治疗的3D-CRT治疗计划，采用VMAT进行SBRT治疗计划并未导致剂量学上的妥协。
