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| ID | Type | Description | Link |
|---|---|---|---|
| 2026-00067 | Other Identifier | BASEC |
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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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| RT with AF | Experimental | Patients with PTV/OAR overlap will receive AF, with dose adapted daily based on anatomy. |
|
| RT without AF | Active Comparator | Patients without PTV/OAR overlap will receive standard fractionated treatment. |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| SBRT with adaptive fractionation | Radiation | 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. |
| Measure | Description | Time Frame |
|---|---|---|
| Proportion of patients with successful daily dose adaptation | Proportion of patients treated with daily dose-adapted treatment, who received at least one fraction of non-uniformly fractionated treatment with expectation of a benefit in PTV-coverage of ≥ 1ccGy | from enrollment to end of treatment at 1-2 weeks |
| Measure | Description | Time Frame |
|---|---|---|
| Acute treatment toxicities | Acute treatment toxicities for all included patients measured with Common Terminology Criteria for Adverse Events | during treatment (1-2 weeks) and until 90 days after |
| Interfractional variation in PTV/OAR overlap volume |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Jan Unkelbach, Prof. Dr. rer. nat. | Contact | +41 44 255 85 49 | jan.unkelbach@usz.ch | |
| Lena Kretzschmar, Dr. med. | Contact | lena.kretzschmar@usz.ch |
| Name | Affiliation | Role |
|---|---|---|
| Reinhardt Krcek, Dr. med. | University of Zurich | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| University Hospital Zurich | Recruiting | Zurich | Canton of Zurich | 8091 | Switzerland |
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| Standard of Care (SOC) | Radiation | 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. |
|
interfractional variation in PTV/OAR overlap volume, in cc
| during treatment (1-2 weeks) |
| Interfractional variation in GTV/OAR distance | interfractional variation in GTV/OAR distance, in mm | during treatment (1-2 weeks) |
| Dosimetric difference in PTV-coverage between algorithm-based calculation and the reference plan | PTV coverage quantified as the area above the dose-volume-histogram curve measured in cc x Gy | after end of treatment (2 weeks after last fraction) |
| ID | Term |
|---|---|
| D000008 | Abdominal Neoplasms |
| D010386 | Pelvic Neoplasms |
| ID | Term |
|---|---|
| D009371 | Neoplasms by Site |
| D009369 | Neoplasms |
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| ID | Term |
|---|---|
| D016634 | Radiosurgery |
| D059039 | Standard of Care |
| ID | Term |
|---|---|
| D011878 | Radiotherapy |
| D013812 | Therapeutics |
| D013238 | Stereotaxic Techniques |
| D019635 | Neurosurgical Procedures |
| D013514 | Surgical Procedures, Operative |
| D008919 | Investigative Techniques |
| D019984 | Quality Indicators, Health Care |
| D011787 | Quality of Health Care |
| D006298 | Health Services Administration |
| D017530 | Health Care Quality, Access, and Evaluation |
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