Lukovic Jelena, Patil Nikhilesh, D'souza David, Millman Barbara, Yaremko Brian P, Leung Eric, Whiston Frances, Hajdok George, Wong Eugene
Department of Radiation Oncology, London Regional Cancer Program, London, Ontario, CA ; Schulich School of Medicine & Dentistry, Western University, London, Ontario, CA.
Nova Scotia Cancer Centre, Nova Scotia Health Authority, Dalhousie University.
Cureus. 2016 Jan 25;8(1):e467. doi: 10.7759/cureus.467.
This study compares dosimetric parameters of planning target volume (PTV) coverage and organs at risk (OAR) sparing when postoperative radiotherapy for gynecologic cancers is delivered using volumetric modulated arc therapy (VMAT) versus a four-field (4FLD) box technique.
From July to December 2012, women requiring postoperative radiation for gynecologic cancers were treated with a standardized VMAT protocol. Two sets of optimized 4FLD plans were retrospectively generated: one based on standard anatomical borders (4FLD) and one based on the clinical target volume (CTV) created for VMAT with a 2 cm expansion guiding field border placement (4FLD+2). Ninety-five percent isodose curves were generated to evaluate PTV coverage.
VMAT significantly improved dose conformity compared with 4FLD and 4FLD+2 plans (p < 0.001) and provided additional coverage of the PTV posteriorly and superiorly, corresponding to coverage of the presacral and proximal iliac vessels. There was a significant reduction in dose to all OARs with VMAT, including a 58% reduction in the volume of the small bowel receiving more than 45 Gy (p=0.005).
Despite treating a larger volume, radiotherapy using a 4FLD technique is less homogenous and provides inferior coverage of the PTV compared with VMAT. With meticulous treatment planning and delivery, VMAT effectively encompasses the PTV and minimizes dose to OARs.
本研究比较了采用容积调强弧形放疗（VMAT）与四野（4FLD）盒式技术进行妇科癌症术后放疗时，计划靶区（PTV）覆盖的剂量学参数以及危及器官（OAR）的受量情况。
2012年7月至12月，对需要进行妇科癌症术后放疗的女性患者采用标准化的VMAT方案进行治疗。回顾性生成两组优化的4FLD计划：一组基于标准解剖边界（4FLD），另一组基于为VMAT创建的临床靶区（CTV）并以2 cm扩展来指导野边界放置（4FLD+2）。生成95%等剂量曲线以评估PTV覆盖情况。
与4FLD和4FLD+2计划相比，VMAT显著改善了剂量适形性（p<0.001），并在PTV的后方和上方提供了额外覆盖，对应于骶前和髂血管近端的覆盖。VMAT使所有OAR的受量显著降低，包括接受超过45 Gy照射的小肠体积减少58%（p=0.005）。
尽管4FLD技术治疗的体积更大，但与VMAT相比，其放疗的均匀性较差，PTV覆盖也欠佳。通过精心的治疗计划和实施，VMAT能有效包绕PTV并使OAR受量最小化。
