Daily Adjustment of the Radiation Dose in MRI-guided Stereotactic Radiotherapy for Tumors in the Abdominal and Pelvic Regions
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- The protocol lists: SBRT with adaptive fractionation, Standard of Care (SOC).
- Who it may be relevant to
- Registry conditions: Abdominal Tumor, Pelvic Tumor. Basic parameters: from 18 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- Switzerland
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
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Official title
Adaptive Fractionation in Online MR-guided SBRT for Abdominal and Pelvic Target Volumes
Overview
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.
Interventions
- Radiation 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. - Radiation 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.
Primary outcome measures
- Proportion of patients with successful daily dose adaptation [Time frame: from enrollment to end of treatment at 1-2 weeks]
Secondary outcome measures (4)
- Acute treatment toxicities [Time frame: during treatment (1-2 weeks) and until 90 days after]
- Interfractional variation in PTV/OAR overlap volume [Time frame: during treatment (1-2 weeks)]
- Interfractional variation in GTV/OAR distance [Time frame: during treatment (1-2 weeks)]
- Dosimetric difference in PTV-coverage between algorithm-based calculation and the reference plan [Time frame: after end of treatment (2 weeks after last fraction)]
Eligibility criteria
Inclusion criteria
- 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
Exclusion criteria
- 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
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: No
Study design
- Allocation
- Non-randomized
- Model
- Parallel assignment
- Masking
- Open label
- Primary purpose
- Treatment
Study locations
Switzerland · 1 center
- University Hospital Zurich — Zurich
Identifiers
NCT: NCT07687147 · RAO-25-019 · 2026-00067