Review of MR-Guided Radiotherapy for Esophageal Cancer

Abstract

In this review, we outline the potential benefits and the future role of MRI and MR-guided radiotherapy (MRgRT) in the management of esophageal cancer. Although not currently used in most clinical practice settings, MRI is a useful non-invasive imaging modality that provides excellent soft tissue contrast and the ability to visualize cancer physiology. Chemoradiation therapy with or without surgery is essential for the management of locally advanced esophageal cancer. MRI can help stage esophageal cancer, delineate the gross tumor volume (GTV), and assess the response to chemoradiotherapy. Integrated MRgRT systems can help overcome the challenge of esophageal motion due to respiratory motion by using real-time imaging and tumor tracking with respiratory gating. With daily on-table MRI, shifts in tumor position and tumor regression can be taken into account for online-adaptation. The combination of accurate GTV visualization, respiratory gating, and online adaptive planning, allows for tighter treatment volumes and improved sparing of the surrounding normal organs. This could lead to a reduction in radiotherapy induced cardiac toxicity, pneumonitis and post-operative complications. Tumor physiology as seen on diffusion weighted imaging or dynamic contrast enhancement can help individualize treatments based on the response to chemoradiotherapy. Patients with a complete response on MRI can be considered for organ preservation while patients with no response can be offered an earlier resection. In patients with a partial response to chemoradiotherapy, areas of residual cancer can be targeted for dose escalation. The tighter and more accurate targeting enabled with MRgRT may enable hypofractionated treatment schedules.

Modern Management of Esophageal Cancer: Radio-Oncology in Neoadjuvancy, Adjuvancy and Palliation

“…Smaller margins may allow for a reduction in the dose to OARs and, therefore, toxicity, such as to the heart, stomach and lungs, which may adversely affect treatment compliance [ 116 ]. Future trials are needed to validate the benefits of MRgRT in esophageal cancer, such as the implementation of the dosimetric benefits of MR-integrated proton therapy (MRIiPT) in a clinical setting [ 122 ].…”

The Role of Magnetic Resonance Imaging in the Management of Esophageal Cancer

“…Finally, MRI-guided radiotherapy for EC remains under development but seems a promising option for the future. The combination of improved GTV delineation, respiratory gating, and online adaptive planning from daily non-irradiating MRI, could allow for tighter target coverage while sparing the adjacent normal organs [ 70 ].…”

Quantifying intrafractional gastric motion using auto‐segmentation on MRI: Deformation and respiratory‐induced displacement compared

“…Inter‐fractional changes in size and shape, due to changes in gastrointestinal filling, can be large 6 and may be managed using image‐guided adaptive RT 7 . This can, for example, be done with a cone‐beam computed tomography (CBCT)‐guided library‐of‐plans approach 8 or on‐line adaptive magnetic resonance imaging (MRI)‐guided RT 9,10 . As also during irradiation changes take place, such as respiratory‐induced motion and peristalsis, these intrafractional changes must be quantified, for example, to establish required RT treatment margins.…”