Ho Hsiu-Wen, Lee Steve P, Lin Hisu-Man, Chen Hsiao-Yun, Huang Chun-Chiao, Wang Shih-Chang, Yang Ching-Chieh, Lin Yu-Wei
Department of Radiation Oncology, Chi Mei Medical Center, No.901, Jhonghua Rd., Yongkang Dist., Tainan City, 71004, Taiwan.
Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
Radiat Oncol. 2020 Jul 8;15(1):164. doi: 10.1186/s13014-020-01602-7.
To evaluate dosimetric differences of salvage irradiations using two commercially available volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) techniques: RapidArc (RA) and HyperArc (HA), for recurrent nasopharyngeal carcinoma (NPC) after initial radiation therapy.
Ten patients with recurrent NPC status previously treated with radiation therapy were considered suitable candidates for salvage SBRT using VMAT approach. Two separate treatment plans were created with HA and RA techniques for each case, with dosimetric outcomes compared with respect to tumor target coverage and organs-at-risk (OARs) sparing. Furthermore, the cumulative radiobiological effects to the relevant OARs from the original radiotherapy to the respective salvage SBRT plans were analyzed in terms of biologically effective dose (BED).
Treatment with HA exhibited similar target dose coverage as with RA, while delivering a higher mean dose to the targets. Using RA technique, the mean maximal doses to optic apparatus and the mean brain dose were reduced by 1 to 1.5 Gy, comparing to HA technique. The conformity index, gradient radius, and intermediate dose spillage in HA plans were significantly better than those in RA. With HA technique, the volume of brain receiving 12 Gy or more was reduced by 44%, comparing to RA technique. The cumulative BEDs to spinal cord and optic apparatus with RA technique were 1 to 2 Gy less than those with HA. HA technique significantly reduced the volume within body that received more than 100 Gy.
With better dose distribution than RA while maintaining sufficient target dose coverage, HA represents an attractive salvage SBRT technique for recurrent NPC.
为评估使用两种商用容积调强弧形放疗（VMAT）立体定向体部放疗（SBRT）技术，即 RapidArc（RA）和 HyperArc（HA），对鼻咽癌（NPC）初治放疗后复发患者进行挽救性放疗时的剂量差异。
10例先前接受过放疗的复发鼻咽癌患者被认为是使用VMAT方法进行挽救性SBRT的合适候选者。针对每个病例，分别使用HA和RA技术创建两个独立的治疗计划，并就肿瘤靶区覆盖和危及器官（OARs）保护方面比较剂量学结果。此外，从生物学有效剂量（BED）角度分析了从原始放疗到各自挽救性SBRT计划对相关OARs的累积放射生物学效应。
HA治疗显示出与RA相似的靶区剂量覆盖，同时向靶区输送更高的平均剂量。与HA技术相比，使用RA技术时，视器的平均最大剂量和平均脑剂量降低了1至1.5 Gy。HA计划中的适形指数、梯度半径和中间剂量溢出明显优于RA计划。与RA技术相比，使用HA技术时，接受12 Gy或更高剂量的脑体积减少了44%。RA技术对脊髓和视器的累积BED比HA技术少1至2 Gy。HA技术显著减少了体内接受超过100 Gy剂量的体积。
HA在保持足够靶区剂量覆盖的同时，具有比RA更好的剂量分布，是复发鼻咽癌一种有吸引力的挽救性SBRT技术。
