Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, FL, USA.
Department of Radiation Oncology, University of Miami Miller School of Medicine, Miami, FL, USA.
Phys Med. 2021 Jan;81:77-85. doi: 10.1016/j.ejmp.2020.11.035. Epub 2021 Jan 11.
To implement a daily CBCT based dose accumulation technique in order to assess ideal robust optimization (RO) parameters for IMPT treatment of prostate cancer.
Ten prostate cancer patients previously treated with VMAT and having daily CBCT were included. First, RO-IMPT plans were created with ± 3 mm and ± 5 mm patient setup and ± 3% proton range uncertainties, respectively. Second, the planning CT (pCT) was deformably registered to the CBCT to create a synthetic CT (sCT). Both daily and weekly sampling strategies were employed to determine optimal dose accumulation frequency. Doses were recalculated on sCTs for both ± 3 mm/±3% and ± 5 mm/±3% uncertainties and were accumulated back to the pCT. Accumulated doses generated from ± 3 mm/±3% and ± 5 mm/±3% RO-IMPT plans were evaluated using the clinical dose volume constraints for CTV, bladder, and rectum.
Daily accumulated dose based on both ± 3mm/±3% and ±5 mm/±3% uncertainties for RO-IMPT plans resulted in satisfactory CTV coverage (RO-IMPT CTV = 99.01 ± 0.87% vs. RO-IMPT CTV = 99.81 ± 0.2%, P = 0.002). However, the accumulated dose based on ± 3 mm/3% RO-IMPT plans consistently provided greater OAR sparing than ±5 mm/±3% RO-IMPT plans (RO-IMPT rectum = 2.93 ± 2.39% vs. RO-IMPT rectum = 4.38 ± 3%, P < 0.01; RO-IMPT bladder = 5.2 ± 7.12% vs. RO-IMPT bladder = 7.12 ± 9.59%, P < 0.01). The gamma analysis showed high dosimetric agreement between weekly and daily accumulated dose distributions.
This study demonstrated that for RO-IMPT optimization, ±3mm/±3% uncertainty is sufficient to create plans that meet desired CTV coverage while achieving superior sparing to OARs when compared with ± 5 mm/±3% uncertainty. Furthermore, weekly dose accumulation can accurately estimate the overall dose delivered to prostate cancer patients.
实施基于每日 CBCT 的剂量积累技术，以评估适形调强质子治疗前列腺癌的理想稳健优化（RO）参数。
纳入 10 例先前接受 VMAT 治疗并每日行 CBCT 的前列腺癌患者。首先，分别采用患者摆位±3mm 和±5mm 以及质子射程±3%不确定性创建 RO-IMPT 计划。其次，将计划 CT（pCT）与 CBCT 进行变形配准以创建合成 CT（sCT）。采用每日和每周采样策略来确定最佳剂量积累频率。在 sCT 上对±3mm/±3%和±5mm/±3%不确定性进行剂量重算，并将其累积回 pCT。基于±3mm/±3%和±5mm/±3%RO-IMPT 计划的累积剂量使用 CTV、膀胱和直肠的临床剂量体积约束进行评估。
基于 RO-IMPT 计划±3mm/±3%和±5mm/±3%不确定性的每日累积剂量导致 CTV 覆盖率令人满意（RO-IMPT CTV=99.01±0.87% vs. RO-IMPT CTV=99.81±0.2%，P=0.002）。然而，基于±3mm/3%RO-IMPT 计划的累积剂量始终比±5mm/±3%RO-IMPT 计划提供更大的 OAR 保护（RO-IMPT 直肠=2.93±2.39% vs. RO-IMPT 直肠=4.38±3%，P<0.01；RO-IMPT 膀胱=5.2±7.12% vs. RO-IMPT 膀胱=7.12±9.59%，P<0.01）。伽马分析显示每周和每日累积剂量分布之间具有高度的剂量一致性。
本研究表明，对于 RO-IMPT 优化，±3mm/±3%的不确定性足以创建满足所需 CTV 覆盖率的计划，同时与±5mm/±3%的不确定性相比，实现对 OAR 的更好保护。此外，每周剂量累积可以准确估计前列腺癌患者的总体剂量。
