Department of Radiation Oncology, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany.
National Center for Radiation Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Im Neuenheimer Feld 400, 69120, Heidelberg, Germany.
Radiat Oncol. 2023 May 29;18(1):92. doi: 10.1186/s13014-023-02284-7.
Re-irradiation is frequently performed in the era of precision oncology, but previous doses to organs-at-risk (OAR) must be assessed to avoid cumulative overdoses. Stereotactic magnetic resonance-guided online adaptive radiotherapy (SMART) enables highly precise ablation of tumors close to OAR. However, OAR doses may change considerably during adaptive treatment, which complicates potential re-irradiation. We aimed to compare the baseline plan with different dose accumulation techniques to inform re-irradiation.
PATIENTS & METHODS: We analyzed 18 patients who received SMART to lung or liver tumors inside prospective databases. Cumulative doses were calculated inside the planning target volumes (PTV) and OAR for the adapted plans and theoretical non-adapted plans via (1) cumulative dose volume histograms (DVH sum plan) and (2) deformable image registration (DIR)-based dose accumulation to planning images (DIR sum plan). We compared cumulative dose parameters between the baseline plan, DVH sum plan and DIR sum plan using equivalent doses in 2 Gy fractions (EQD2).
Individual patients presented relevant increases of near-maximum doses inside the proximal bronchial tree, spinal cord, heart and gastrointestinal OAR when comparing adaptive treatment to the baseline plans. The spinal cord near-maximum doses were significantly increased in the liver patients (D2% median: baseline 6.1 Gy, DIR sum 8.1 Gy, DVH sum 8.4 Gy, p = 0.04; D0.1 cm³ median: baseline 6.1 Gy, DIR sum 8.1 Gy, DVH sum 8.5 Gy, p = 0.04). Three OAR overdoses occurred during adaptive treatment (DIR sum: 1, DVH sum: 2), and four more intense OAR overdoses would have occurred during non-adaptive treatment (DIR sum: 4, DVH sum: 3). Adaptive treatment maintained similar PTV coverages to the baseline plans, while non-adaptive treatment yielded significantly worse PTV coverages in the lung (D95% median: baseline 86.4 Gy, DIR sum 82.4 Gy, DVH sum 82.2 Gy, p = 0.006) and liver patients (D95% median: baseline 87.4 Gy, DIR sum 82.1 Gy, DVH sum 81.1 Gy, p = 0.04).
OAR doses can increase during SMART, so that re-irradiation should be planned based on dose accumulations of the adapted plans instead of the baseline plan. Cumulative dose volume histograms represent a simple and conservative dose accumulation strategy.
在精准肿瘤学时代，经常进行再照射，但必须评估先前的器官危险（OAR）剂量，以避免累积剂量过高。立体定向磁共振引导在线自适应放疗（SMART）可实现对靠近 OAR 的肿瘤进行高度精确的消融。然而，在自适应治疗过程中，OAR 剂量可能会发生很大变化，这使得潜在的再照射复杂化。我们旨在比较基线计划与不同的剂量累积技术，以提供再照射信息。
我们分析了 18 名在肺或肝肿瘤接受 SMART 治疗的患者，这些患者来自前瞻性数据库。通过（1）累积剂量体积直方图（DVH sum plan）和（2）基于变形图像配准（DIR）的剂量累积到计划图像（DIR sum plan），在计划靶区（PTV）和 OAR 内为适应治疗和理论非适应治疗计算累积剂量。我们使用等效 2 Gy 分数剂量（EQD2）比较基线计划、DVH sum plan 和 DIR sum plan 之间的累积剂量参数。
与基线计划相比，个别患者在近端支气管树、脊髓、心脏和胃肠道 OAR 中观察到适应治疗时接近最大剂量的明显增加。肝脏患者的脊髓近最大剂量明显增加（D2%中位数：基线 6.1 Gy，DIR sum 8.1 Gy，DVH sum 8.4 Gy，p=0.04；D0.1 cm³中位数：基线 6.1 Gy，DIR sum 8.1 Gy，DVH sum 8.5 Gy，p=0.04）。在自适应治疗过程中发生了 3 次 OAR 剂量过高（DIR sum：1 次，DVH sum：2 次），如果进行非自适应治疗，则会发生 4 次更严重的 OAR 剂量过高（DIR sum：4 次，DVH sum：3 次）。自适应治疗与基线计划相比，保持了相似的 PTV 覆盖率，而非自适应治疗在肺（D95%中位数：基线 86.4 Gy，DIR sum 82.4 Gy，DVH sum 82.2 Gy，p=0.006）和肝患者（D95%中位数：基线 87.4 Gy，DIR sum 82.1 Gy，DVH sum 81.1 Gy，p=0.04）中产生了显著更差的 PTV 覆盖率。
在 SMART 中，OAR 剂量可能会增加，因此再照射应基于适应计划的剂量累积，而不是基线计划。累积剂量体积直方图代表了一种简单保守的剂量累积策略。
