Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee.
Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee.
Int J Radiat Oncol Biol Phys. 2021 Jan 1;109(1):242-251. doi: 10.1016/j.ijrobp.2020.08.036. Epub 2020 Oct 28.
Pencil-beam scanning proton therapy is particularly sensitive to anatomic changes, which may affect the delivered dose distribution. This study examined whether offline adaptation using on-treatment magnetic resonance imaging (MRI) scan during proton therapy could improve plan quality for pediatric patients.
Pediatric patients with at least 1 MRI scan in the treatment position (MRI) during proton therapy between January 2017 and July 2019 were retrospectively reviewed. Patients underwent MRI and computed tomography simulation. Cases were planned with scenario-based optimization with 3 mm/3% positional/range uncertainty. Patients demonstrating anatomic change on MRI were recontoured. The original plans were applied to the anatomy-of-the-day for dose recalculation (delivered plans). Plans were subsequently reoptimized offline, using original beam angles and dose-volume constraints (adapted plans). Delivered plans were compared with adapted plans to detect significant changes in plan quality, defined as a ≥5% decrease in the clinical target volume (CTV) receiving 95% of the prescription dose (V95) or a ≥5% increase in the dose-volume parameter used as an organ-at-risk constraint.
Seventy-three pediatric patients were eligible, with 303 MRI scans (73 simulation and 230 MRI scans) available for analysis. The median MRI scans per patient was 3 (range, 1-7). Twenty patients (27%) showed anatomic change, with 11 (55%) demonstrating a significant change in delivered plan quality. Significant changes were noted on MRI from week 2 (n = 3) or week 3 (n = 8). Seven of these 11 patients (64%) had a significantly reduced CTV V95 (median decrease, 7.6%; range, 5%-16%). Four (36%) had a significantly increased dose to the brain stem, hippocampus, and/or optic apparatus. Eight had a suprasellar low-grade glioma or head and neck rhabdomyosarcoma.
On-treatment MRI was useful in detecting anatomic changes during proton therapy. MRI-based offline adaptation improved plan quality for most patients with anatomic changes. Further studies should determine the clinical value of MRI-based adaptive therapy for pediatric patients.
铅笔束扫描质子治疗对解剖结构的变化特别敏感，这可能会影响所给予的剂量分布。本研究旨在探讨质子治疗过程中使用治疗中磁共振成像（MRI）扫描进行离线自适应是否可以改善儿科患者的计划质量。
回顾性分析了 2017 年 1 月至 2019 年 7 月期间至少有 1 次在质子治疗中接受治疗体位 MRI（MRI）扫描的儿科患者。患者进行了 MRI 和计算机断层扫描模拟。采用基于场景的优化方法进行计划制定，设定 3mm/3%的位置/范围不确定性。对 MRI 上显示解剖结构变化的患者进行重新轮廓勾画。将原始计划应用于当天的解剖结构进行剂量重新计算（已交付计划）。随后，使用原始射束角度和剂量-体积限制（自适应计划）对计划进行离线重新优化。将已交付的计划与自适应计划进行比较，以检测计划质量的显著变化，定义为临床靶体积（CTV）接受 95%处方剂量（V95）的减少≥5%，或作为危及器官限制的剂量-体积参数的增加≥5%。
共有 73 名儿科患者符合条件，共 303 次 MRI 扫描（73 次模拟和 230 次 MRI 扫描）可用于分析。每位患者的中位数 MRI 扫描次数为 3 次（范围为 1-7 次）。20 名患者（27%）显示解剖结构变化，其中 11 名（55%）的已交付计划质量发生显著变化。在第 2 周（n=3）或第 3 周（n=8）的 MRI 上观察到显著变化。这 11 名患者中的 7 名（64%）CTV V95 显著降低（中位数降低 7.6%；范围 5%-16%）。4 名（36%）脑干、海马体和/或视神经的剂量显著增加。8 名患者患有鞍上低度胶质瘤或头颈部横纹肌肉瘤。
治疗中 MRI 有助于在质子治疗过程中检测解剖结构的变化。基于 MRI 的离线自适应可改善大多数发生解剖结构变化患者的计划质量。进一步的研究应确定基于 MRI 的自适应治疗对儿科患者的临床价值。
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