Hoegen-Saßmannshausen Philipp, Hartschuh Tobias P, Renkamp Claudia Katharina, Buchele Carolin, Schlüter Fabian, Sandrini Elisabetta, Weykamp Fabian, Regnery Sebastian, Meixner Eva, König Laila, Debus Jürgen, Klüter Sebastian, Hörner-Rieber Juliane
Department of Radiation Oncology, Heidelberg University Hospital, 69210 Heidelberg, Germany.
Heidelberg Institute of Radiation Oncology (HIRO), 69120 Heidelberg, Germany.
Cancers (Basel). 2025 Apr 30;17(9):1533. doi: 10.3390/cancers17091533.
BACKGROUND/OBJECTIVES: Stereotactic body radiotherapy is frequently used in patients with adrenal metastases. Motion of adherent radiosensitive organs at risk (OARs) and tumors influence OAR toxicity and tumor control. Online-adaptive Magnetic Resonance-guided radiotherapy (MRgRT) can address and mitigate interfractional changes. However, the impact of intrafractional variations in adrenal MRgRT is unknown.
A total of 23 patients with 24 adrenal metastases were treated with MRgRT. After daily plan adaptation and before beam application, an additional (preRT) 3d MRI was acquired. PreRT target volumes and OARs were retrospectively recontoured in 200 fractions. The delivered, online-adapted treatment plans, as well as non-adapted baseline plans, were calculated on these re-contoured structures to quantify the dosimetric impact of intrafractional variations on target volume coverage and OAR doses with and without online adaptation. Normal tissue complication probabilities (NTCPs) were calculated.
The median time between the two MRIs was 56.4 min. GTV and PTV coverage (dose to 95% of the PTV, D95%, and volume covered by 100% of the prescription dose, V100%) were significantly inferior in the preRT plans. GTV D was significantly impaired in left-sided metastases, but not in right-sided metastases. Compared to non-adapted preRT plans, adapted preRT plans were still significantly superior for all GTV and PTV metrics. Intrafractional violations of OAR constraints were frequent. D0.5cc and the volume exposed to the near-maximum dose constraint were significantly higher in the preRT plans. The volume exposed to the D0.5cc constraints in single fractions escalated up to 1.5 cc for the esophagus, 3.2 cc for the stomach, 5.3 cc for the duodenum and 7.3 cc for the bowel. This led to significantly elevated NTCPs for the stomach, bowel and duodenum. Neither PTV D95%, nor gastrointestinal OAR maximum doses were significantly impaired by longer fraction duration.
Intrafractional motion in adrenal MRgRT caused significant impairment of target volume coverage (D95% and V100%), potentially undermining local control. Frequent violation of gastrointestinal OAR constraints led to elevated NTCP. Compared to non-adaptive treatment, online adaptation still highly improved GTV and PTV coverage.
背景/目的：立体定向体部放疗常用于肾上腺转移瘤患者。有放射敏感性的危及器官（OARs）和肿瘤的运动影响OAR毒性和肿瘤控制。在线自适应磁共振引导放疗（MRgRT）可以解决并减轻分次间的变化。然而，肾上腺MRgRT中分次内变化的影响尚不清楚。
共有23例患有24个肾上腺转移瘤的患者接受了MRgRT治疗。在每日计划调整后且在束流照射前，采集一次额外的（放疗前）三维MRI。在200个分次中对放疗前的靶区体积和OARs进行回顾性重新勾画。在这些重新勾画的结构上计算已实施的、在线调整后的治疗计划以及未调整的基线计划，以量化分次内变化对靶区体积覆盖和OAR剂量的剂量学影响，包括有无在线调整的情况。计算正常组织并发症概率（NTCPs）。
两次MRI之间的中位时间为56.4分钟。放疗前计划中的大体肿瘤体积（GTV）和计划靶体积（PTV）覆盖情况（PTV的95%剂量，D95%，以及100%处方剂量覆盖的体积，V100%）明显较差。左侧转移瘤的GTV剂量明显受损，但右侧转移瘤则不然。与未调整的放疗前计划相比，调整后的放疗前计划在所有GTV和PTV指标上仍明显更优。分次内违反OAR约束的情况很常见。放疗前计划中的D0.5cc和接近最大剂量约束下暴露的体积明显更高。单次分次中暴露于D0.5cc约束下的体积，食管可达1.5cc，胃可达3.2cc，十二指肠可达5.3cc，肠可达7.3cc。这导致胃、肠和十二指肠的NTCPs明显升高。分次持续时间延长对PTV D95%和胃肠道OAR最大剂量均无明显影响。
肾上腺MRgRT中的分次内运动导致靶区体积覆盖（D95%和V100%）明显受损，可能会破坏局部控制。频繁违反胃肠道OAR约束导致NTCP升高。与非自适应治疗相比，在线调整仍能显著改善GTV和PTV覆盖情况。
