Henke Lauren, Kashani Rojano, Yang Deshan, Zhao Tianyu, Green Olga, Olsen Lindsey, Rodriguez Vivian, Wooten H Omar, Li H Harold, Hu Yanle, Bradley Jeffrey, Robinson Clifford, Parikh Parag, Michalski Jeff, Mutic Sasa, Olsen Jeffrey R
Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri.
Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado.
Int J Radiat Oncol Biol Phys. 2016 Dec 1;96(5):1078-1086. doi: 10.1016/j.ijrobp.2016.08.036. Epub 2016 Aug 31.
To characterize potential advantages of online-adaptive magnetic resonance (MR)-guided stereotactic body radiation therapy (SBRT) to treat oligometastatic disease of the non-liver abdomen and central thorax.
Ten patients treated with RT for unresectable primary or oligometastatic disease of the non-liver abdomen (n=5) or central thorax (n=5) underwent imaging throughout treatment on a clinical MR image guided RT system. The SBRT plans were created on the basis of tumor/organ at risk (OAR) anatomy at initial computed tomography simulation (P), and simulated adaptive plans were created on the basis of observed MR image set tumor/OAR "anatomy of the day" (P). Each P was planned under workflow constraints to simulate online-adaptive RT. Prescribed dose was 50 Gy/5 fractions, with goal coverage of 95% planning target volume (PTV) by 95% of the prescription, subject to hard OAR constraints. The P was applied to each MR dataset and compared with P to evaluate changes in dose delivered to tumor/OARs, with dose escalation when possible.
Hard OAR constraints were met for all P based on anatomy from initial computed tomography simulation, and all P based on anatomy from each daily MR image set. Application of the P to anatomy of the day caused OAR constraint violation in 19 of 30 cases. Adaptive planning increased PTV coverage in 21 of 30 cases, including 14 cases in which hard OAR constraints were violated by the nonadaptive plan. For 9 P cases, decreased PTV coverage was required to meet hard OAR constraints that would have been violated in a nonadaptive setting.
Online-adaptive MRI-guided SBRT may allow PTV dose escalation and/or simultaneous OAR sparing compared with nonadaptive SBRT. A prospective clinical trial is underway at our institution to evaluate clinical outcomes of this technique.
描述在线自适应磁共振（MR）引导的立体定向体部放射治疗（SBRT）在治疗非肝脏腹部和中央胸部寡转移疾病方面的潜在优势。
10例因不可切除的原发性或非肝脏腹部（n = 5）或中央胸部（n = 5）寡转移疾病接受放疗的患者，在临床MR图像引导放疗系统上进行了整个治疗过程的成像。SBRT计划是根据初始计算机断层扫描模拟（P）时的肿瘤/危及器官（OAR）解剖结构制定的，模拟自适应计划是根据观察到的MR图像集肿瘤/OAR“当日解剖结构”（P）制定的。每个P在工作流程限制下进行规划，以模拟在线自适应放疗。处方剂量为50 Gy/5次分割，目标是95%的处方剂量覆盖95%的计划靶体积（PTV），同时遵守严格的OAR限制。将P应用于每个MR数据集，并与P进行比较，以评估肿瘤/OAR所接受剂量的变化，如有可能则进行剂量递增。
基于初始计算机断层扫描模拟的解剖结构，所有P均满足严格的OAR限制，基于每日MR图像集解剖结构的所有P也均满足。将P应用于当日解剖结构时，30例中有19例出现OAR限制违反情况。自适应规划使30例中的21例PTV覆盖率增加，其中14例非自适应计划违反了严格的OAR限制。对于9例P，为了满足在非自适应情况下会被违反的严格OAR限制，需要降低PTV覆盖率。
与非自适应SBRT相比，在线自适应MRI引导的SBRT可能允许PTV剂量递增和/或同时减少OAR受量。我们机构正在进行一项前瞻性临床试验，以评估该技术的临床疗效。
