MR-informed Stereotactic Radiotherapy for Treatment of Ultracentral Lung Tumours Utilising a Dedicated MR-simulator for Daily Adaptation Followed by CBCT-guided Treatment Delivery

Summary

Stereotactic body radiotherapy (SBRT) is the preferred treatment for inoperable early-stage non-small cell lung cancer (NSCLC) and for operable cases when patients decline surgery, offering local control (LC) rates of 80-97%. SBRT is also used in oligometastatic cancer. However, its safety and efficacy for ultra-central lung tumours, near the proximal bronchial tree (PBT) and/or esophagus, remain debated. SBRT targeting these tumours has been associated with higher risk of severe toxicity, including pulmonary hemorrhage and pneumonitis. The term "ultra-central lung tumours" refers to tumours abutting the PBT, trachea, or esophagus. 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 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-linac systems and the demands for staffing resources of MR-linacs are limiting a broader implementation of this technology. The MAGELLAN trial is currently investigating MR-linac based SBRT in ultracentral lung tumours to reduce severe toxicity, with outcomes pending. At the Department of Radiation Oncology, University Hospital Zurich, MRI-simulations for RT planning using a dedicated scanner have been performed since 2023 for different tumour entities. We have developed and implemented an MRI-based RT online adaptive re-planning workflow followed by RT delivered at a CBCT-guided, conventional linac. We now aim to expand this MR-informed workflow to online adaptive RT for ultracentral lung tumours. With this study, we will investigate the feasibility of MR-informed, online adaptive SBRT for ultracentral lung tumours using a dedicated MR simulator and treatment delivery using conventional CBCT-linac technology.

Eligibility

Inclusion Criteria:

* Written informed consent according to Swiss law and ICH/GCP regulations signed and dated by the participant and the investigator before any trial specific procedures (Informed Consent Form);
* Ultracentral (PTV-overlap with bronchial tree, trachea/carina and/or esophagus) primary or secondary lung lesion(s) from a histologically confirmed malignancy, confirmed by imaging and amenable for SBRT;
* Indication for SBRT based on a multidisciplinary tumour board recommendation and / or clinical practice guideline;
* Age≥18 years old;
* Patients who are willing and able to comply with scheduled visits, treatment, and other trial procedures.

Exclusion Criteria:

* Large body size that would not fit the MRI-simulator bore;
* Contraindications for MRI;
* Previous radiation therapy directly overlapping with planned SBRT (type I re-irradiation);
* Women who are pregnant or breast feeding;
* Intention to become pregnant during the trial;
* Lack of safe contraception (Female participants who underwent hysterectomy and/or bilateral oophorectomy or post-menopausal for longer than 2 years are not considered as being of child bearing potential);
* Known or suspected non-compliance, drug or alcohol abuse;
* Inability to follow the procedures of the trial, e.g. due to language problems of the participant;
* Enrolment of the investigator, his/her family members, employees and other dependent persons.

Conditions3

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