Daily Adjustment of the Radiation Dose in MRI-guided Stereotactic Radiotherapy for Tumors in the Abdominal and Pelvic Regions

Официальное название

Adaptive Fractionation in Online MR-guided SBRT for Abdominal and Pelvic Target Volumes

Обзор

SBRT delivers high-dose radiation to precisely defined target volumes and is an effective locally ablative treatment option for both primary tumours and oligometastases in various settings, including lesions in the abdomen or pelvis. However, SBRT in these regions faces considerable challenges such as inter-fractional organ motion and anatomical deformation, which can compromise treatment precision. MR-guided SBRT offers a solution, providing superior soft-tissue contrast and enabling real-time, online treatment plan adaptation over the course of SBRT. This approach reduces the risk of geographical miss and overdose to adjacent, vulnerable OARs. Currently, MR-guided SBRT uses a fixed dose per fraction, only adjusting target volume and OAR contours for anatomical changes when performing plan adaptation. However, overlaps between planning target volumes (PTVs) and dose-limiting OARs regularly require compromises in PTV coverage. To address this, AF aims to also adjust dose per fraction based on daily PTV-OAR overlap. With this approach, more dose is applied on treatment days with less PTV-OAR overlap while less dose is applied on days with more PTV-OAR overlap. This trial assesses the feasibility of AF in MR-guided SBRT for abdominal and pelvic tumours that show PTV-overlap with one or more dose-limiting OARs, ultimately aiming to enhance PTV dose coverage without increasing toxicity.

Вмешательства

• Лучевая терапия SBRT with adaptive fractionation
  The fraction dose to the PTV will be adapted based on the volume overlap of PTV and the dose-limiting OAR(s) (bowel / duodenum / stomach) on the planning MRI scan of the day ("geometry-of-the-day"). The treatment plan is then approved by the treating physician and independently verified according to department-internal standard. MR-guided fraction dose adaptation will be repeated at each of the 5 fractions, until the prescribed total dose is reached.
• Лучевая терапия Standard of Care (SOC)
  Patients that qualify for inclusion in the study but for whom AF is no viable treatment due to lacking PTV/OAR overlap in the planning scans. These patients are treated according to clinical standard of care (SoC), i.e. without dose adaptation, and function as a control group.

Первичные конечные точки

• Proportion of patients with successful daily dose adaptation [Срок оценки: from enrollment to end of treatment at 1-2 weeks]

Вторичные конечные точки (4)

• Acute treatment toxicities [Срок оценки: during treatment (1-2 weeks) and until 90 days after]
• Interfractional variation in PTV/OAR overlap volume [Срок оценки: during treatment (1-2 weeks)]
• Interfractional variation in GTV/OAR distance [Срок оценки: during treatment (1-2 weeks)]
• Dosimetric difference in PTV-coverage between algorithm-based calculation and the reference plan [Срок оценки: after end of treatment (2 weeks after last fraction)]

Критерии участия

Критерии включения

• Karnofsky performance status ≥70
• Abdominal or pelvic malignancy (primary or secondary) with previous histological confirmation of the primary tumour, amenable to SBRT in 5 fractions (excluding SBRT to primary tumour in patients with prostate cancer) Note: patients with primary prostate cancer are eligible, but SBRT to the primary tumour in the prostate cannot be performed within the study
• Total prescribed SBRT dose > 30 Gy (constraint for dose-limiting OAR) over 5 treatment fractions
• Distance of the GTV ≤ 1 cm from at least one dose-limiting OAR (bowel / duodenum / stomach) in the available diagnostic images
• Patients able to tolerate long (approximately 60 minutes) treatment time according to clinical evaluation of the treating radiation oncologist
• Patients willing and able to comply with scheduled visits, treatment, and other trial procedures

Критерии исключения

• Previous radiation therapy directly overlapping with planned SBRT (type I re-irradiation)
• More than one PTV irradiated in the same plan
• Contraindications for MRI, e.g., patients with metal fragments or implanted devices that are not MR compatible such as certain types of pacemakers and aneurysm clips or severe claustrophobia
• SBRT not indicated or not possible
• Inability to follow the procedures of the trial, e.g. due to language problems of the participant

Критерии приведены из реестра в оригинале (на английском). Окончательную оценку соответствия проводит исследовательский центр.

Здоровые добровольцы: Нет

Дизайн исследования

Распределение

Нерандомизированное

Модель

Параллельные группы

Маскирование

Открытое

Основная цель

Лечение

Центры проведения

Швейцария · 1 центр

• University Hospital Zurich — Zurich

Идентификаторы

NCT: NCT07687147 · RAO-25-019 · 2026-00067

Первоисточники (государственные реестры)

• ClinicalTrials.gov (NIH, США)

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