Visak Justin, McGarry Ronald C, Randall Marcus E, Pokhrel Damodar
Medical Physics Graduate Program, Department of Radiation Medicine, University Kentucky, Lexington, KY, USA.
J Appl Clin Med Phys. 2021 Jan;22(1):146-155. doi: 10.1002/acm2.13120. Epub 2020 Dec 7.
To develop a robust and adaptable knowledge-based planning (KBP) model with commercially available RapidPlan for early stage, centrally located non-small-cell lung tumors (NSCLC) treated with stereotactic body radiotherapy (SBRT) and improve a patient's"simulation to treatment" time.
The KBP model was trained using 86 clinically treated high-quality non-coplanar volumetric modulated arc therapy (n-VMAT) lung SBRT plans with delivered prescriptions of 50 or 55 Gy in 5 fractions. Another 20 independent clinical n-VMAT plans were used for validation of the model. KBP and n-VMAT plans were compared via Radiation Therapy Oncology Group (RTOG)-0813 protocol compliance criteria for conformity (CI), gradient index (GI), maximal dose 2 cm away from the target in any direction (D2cm), dose to organs-at-risk (OAR), treatment delivery efficiency, and accuracy. KBP plans were re-optimized with larger calculation grid size (CGS) of 2.5 mm to assess feasibility of rapid adaptive re-planning.
Knowledge-based plans were similar or better than n-VMAT plans based on a range of target coverage and OAR metrics. Planning target volume (PTV) for validation cases was 30.5 ± 19.1 cc (range 7.0-71.7 cc). KBPs provided an average CI of 1.04 ± 0.04 (0.97-1.11) vs. n-VMAT plan'saverage CI of 1.01 ± 0.04 (0.97-1.17) (P < 0.05) with slightly improved GI with KBPs (P < 0.05). D2cm was similar between the KBPs and n-VMAT plans. KBPs provided lower lung V10Gy (P = 0.003), V20Gy (P = 0.007), and mean lung dose (P < 0.001). KBPs had overall better sparing of OAR at the minimal increased of average total monitor units and beam-on time by 460 (P < 0.05) and 19.2 s, respectively. Quality assurance phantom measurement showed similar treatment delivery accuracy. Utilizing a CGS of 2.5 mm in the final optimization improved planning time (mean, 5 min) with minimal or no cost to the plan quality.
The RTOG-compliant adaptable RapidPlan model for early stage SBRT treatment of centrally located lung tumors was developed. All plans met RTOG dosimetric requirements in less than 30 min of planning time, potentially offering shorter "simulation to treatment" times. OAR sparing via KBPs may permit tumorcidal dose escalation with minimal penalties. Same day adaptive re-planning is plausible with a 2.5-mm CGS optimizer setting.
利用商用的RapidPlan开发一种强大且适应性强的基于知识的计划（KBP）模型，用于早期、位于中央的非小细胞肺癌（NSCLC）的立体定向体部放疗（SBRT），并缩短患者的“模拟到治疗”时间。
使用86个临床治疗的高质量非共面容积调强弧形放疗（n-VMAT）肺部SBRT计划训练KBP模型，这些计划的处方剂量为50或55 Gy，分5次给予。另外20个独立的临床n-VMAT计划用于模型验证。通过放射治疗肿瘤学组（RTOG）-0813协议的适形性（CI）、梯度指数（GI）、在任何方向距靶区2 cm处的最大剂量（D2cm）、危及器官（OAR）的剂量、治疗实施效率和准确性等标准，对KBP计划和n-VMAT计划进行比较。使用2.5 mm的更大计算网格尺寸（CGS）对KBP计划进行重新优化，以评估快速自适应重新计划的可行性。
基于一系列靶区覆盖和OAR指标，基于知识的计划与n-VMAT计划相似或更好。验证病例的计划靶体积（PTV）为30.5±19.1 cc（范围7.0 - 71.7 cc）。KBP计划的平均CI为1.04±0.04（0.97 - 1.11），而n-VMAT计划的平均CI为1.01±0.04（0.97 - 1.17）（P < 0.05），KBP计划的GI略有改善（P < 0.05）。KBP计划和n-VMAT计划的D2cm相似。KBP计划的肺V10Gy（P = 0.003）、V20Gy（P = 0.007）和平均肺剂量更低（P < 0.001）。KBP计划在平均总监测单位和照射时间分别仅增加460（P < 0.05）和19.2 s的情况下，对OAR的总体保护更好。质量保证体模测量显示治疗实施准确性相似。在最终优化中使用2.5 mm的CGS可缩短计划时间（平均5分钟），且对计划质量的影响最小或无影响。
开发了符合RTOG标准的适用于早期SBRT治疗中央型肺部肿瘤的适应性RapidPlan模型。所有计划在不到30分钟的计划时间内均满足RTOG剂量学要求，可能提供更短的“模拟到治疗”时间。通过KBP计划对OAR的保护可能允许在最小代价下提高肿瘤杀灭剂量。使用2.5 mm CGS优化器设置进行当日自适应重新计划是可行的。
