Magnetic Resonance Imaging-guided Online Adaptive Radiotherapy of Pelvic Lymph Node Metastases (MACULA)

Magnetic Resonance Imaging-guided Online Adaptive Radiotherapy Using a Dedicated MR-simulator and a Cone Beam CT Based Treatment Delivery for Stereotactic Body Radiation Therapy of Pelvic Lymph Node Metastases (MACULA-Trial)

In this study, the investigators want to investigate whether online-adapted radiotherapy using a special magnetic resonance imaging (MRI) simulator and computed tomography (CT)-guided radiation therapy, is feasible and offers advantages for the treatment of pelvic lymph node metastases.

Study Overview

• Status: Active, not recruiting
• Conditions: Pelvic and Para-aortic Lymph Node Metastases
• Intervention / Treatment: Radiation: Magnetic resonance Imaging-guided online adaptive radiotherapy

Detailed Description

MR-guided online adaptive radiotherapy has been implemented recently using MR-linac technology, where MR-imaging is combined with linac technology in hybrid systems. These systems offer MR imaging for online adaptive radiotherapy (RT) within the treatment room and with the patient in treatment position. Despite results regarding technical and clinical feasibility being promising, the high costs of MR-linacs systems and the high demands for staffing resources of MR-linacs are limiting a boarder implementation of this technology. At the Department of Radiation Oncology, University Hospital Zurich, MRI-simulations for RT planning using a dedicated scanner have been performed since 2023. The investigators have developed and implemented an MRI-only RT planning workflow followed by RT delivered at a CBCT-guided, conventional linac. The aim to expand the MRI-only workflow to online adaptive RT. This study will investigate the feasibility of MRI-guided, online adaptive SBRT for pelvic and para-aortic lymph node metastases using a dedicated MR simulator and treatment delivery using conventional CBCT-linac technology.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Switzerland
  • Canton of Zurich
    • Zurich, Canton of Zurich, Switzerland, 8091
      • Zurich University Hospital, Department of Radiation Oncology

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Intra-pelvic and para-aortic lymph node metastases from a histologically confirmed malignancy;
• Indication for SBRT based on a multidisciplinary tumor board recommendation and / or clinical practice guideline;
• Intra-pelvic and para-aortic lymph node metastases confirmed by imaging and amenable for SBRT

Exclusion Criteria:

• Large body size that would not fit the MRI-simulator bore;

• Contraindications for MRI including but not limited to

  • electronic devices such as pacemakers, defibrillators, deep brain stimulators, cochlear implants that are labeled as MR unsafe. Electronic devices labeled as MR safe or MR conditional are not a contraindication;
  • metallic foreign body in the eye or aneurysm clips in the brain;
  • severe claustrophobia;
  • hip prosthesis that are labeled as MR unsafe;
• More than 5 pelvic lymph node metastasis
• Previous radiation therapy directly overlapping with SBRT in this study and leading to exceeding tolerance of OARs;
• History of Crohn's disease, ulcerative colitis

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: MR-guided online adaptive RT using a dedicated MR-simulator and cone-beam CT (CBCT)-based treatment

Radiation: Magnetic resonance Imaging-guided online adaptive radiotherapy; On each day of treatment, a new MRI scan in the treatment position will be acquired using the dedicated MR simulator, co-registered with the original one. The original target and organ at risk (OAR) contours will be propagated to the new image set using rigid and deformable image registration. The contours will be adapted to changes detected with MRI of the day. The original SBRT treatment plan will be adapted to the changed and hence adapted anatomy of targets and OARs by plan optimization. Dose calculation will be performed on the newly generated synthetic CT (preferred) or, if there is a contra-indication for synthetic CT, on the original image.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rate of successfully delivered fractions	Feasibility is measured as a successful delivery of an MRI-adapted plan using CBCT image-guidance in another room in 90% of the SBRT fractions.	during treatment, 1-2 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Average improvement of coverage of planning target volume	Dosimetric advantage is defined as >5% improvement in coverage of the planning target volume (PTV) or >5% better sparing of one of the organs at risk (bowel, sigma , rectum, bladder).	During treatment, 1-2 weeks
Adverse Events	Common Terminology Criteria for Adverse Events (CTCAE), version 5.0	during SBRT, 3 months and 24 months of follow-up

Collaborators and Investigators

• Sponsor: University of Zurich

Study record dates

Study Major Dates

• Study Start (Actual): July 16, 2025
• Primary Completion (Actual): January 26, 2026
• Study Completion (Estimated): January 26, 2028

Study Registration Dates

• First Submitted: July 3, 2025
• First Submitted That Met QC Criteria: July 16, 2025
• First Posted (Actual): July 24, 2025

Study Record Updates

• Last Update Posted (Actual): May 11, 2026
• Last Update Submitted That Met QC Criteria: May 8, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: pelvic; lymph node; para-aortic
• Additional Relevant MeSH Terms: Pathologic Processes; Neoplasms; Neoplastic Processes; Neoplasm Metastasis; Lymphatic Metastasis
• Other Study ID Numbers: RAO-24-017

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No