The Role of MRI-Guided Radiation Therapy for Palliation of Mobile Abdominal Cancers: A Report of Two Cases

ABSTRACT Clinical use of and indications for magnetic-resonance image-guided radiotherapy (MRgRT) have expanded since its first clinical implementation in 2014. However, in present implementation, it is a resource-intense treatment modality, often requiring physician and physicist presence at the treatment console. It is therefore most commonly utilized for advanced practice radiotherapy techniques such as online adaptive radiotherapy and stereotactic body radiotherapy with reduced treatment margins. In contrast, image guidance for palliative radiotherapy typically comprises simple x-ray imaging for bony anatomic patient alignment at the first fraction, with only rudimentary alignment procedures for subsequent fractions. However, the high-quality on-board imaging inherent to MRgRT as well as the opportunity for flexible on-table plan adaptation may also have a role for select palliative treatment cases. We present two cases where standard x-ray image guidance would have failed due to abdominal target mobility, and where MRI-guided radiotherapy with online plan adaptation enabled effective treatment.