The Sylvester Comprehensive Cancer Center MRI-Guided Radiotherapy Program: The Next Frontier in Radiation Oncology

In the continued endeavor to improve targeting accuracy, radiation oncology has come a long way over the years. From film x-rays and skin marks to fiducials and cone-beam computed tomography (CBCT), we’ve seen improvements in patient alignment and tumor localization. Yet an unmet need still existed for more accurate soft-tissue visualization during radiation therapy treatment and capabilities that would enable truly adaptive delivery. 

As the clinically preferred method of visualizing soft tissue for diagnostic purposes, magnetic resonance imaging (MRI) is a natural choice. It provides high-contrast images and doesn’t expose patients to unnecessary ionizing radiation. MRI was traditionally incompatible with radiation treatment delivery due to interference between the magnet and the photon beam. The MRIdian system (ViewRay) is the world’s first and only clinical MRI-guided radiation therapy system. It provides a unique combination of simultaneous radiation therapy delivery and continuous MR imaging for the treatment of cancer.

The radiation oncology team at the Sylvester Comprehensive Cancer Center, part of UHealth - University of Miami Health System, has always believed in the importance of integrating advanced imaging techniques into clinical practice and research. Therefore, MRI-guided radiotherapy was a logical addition to our radiation oncology offerings. We installed our MRIdian system in March 2016 and patient treatments began in mid April 2016, making us the fourth hospital in the United States and the first on the east coast to acquire a MRIdian System.

Compared to CBCT, which is the technology used for daily set-up on linear accelerators, MRI-guided radiation therapy provides more accurate daily set-up for most tumor sites. In addition, this system opens the door to an entirely new way of seeing what happens between and during treatments in regard to patient anatomy and the changes that take place. Because MRI technology eliminates the radiation exposure associated with CT scans, the MRIdian system allows for continuous imaging during the delivery of radiation therapy. We can see clearly the target and watch where the radiation dose is actually being delivered in real time (Figures 1 and 2).

One of the most impactful aspects of MRIdian is its adaptive therapy capabilities, which allow radiation oncologists to adapt the treatment plan and delivery based on changes in the tumor and surrounding tissues on a daily basis. We can now account for factors like tumor shrinkage and changes in anatomy of distensible or mobile structures such as the bladder, rectum, and stomach – all of which can change significantly between offline plan creation and the start of each treatment. MRIdian treatment planning software lets us review and adapt the treatment plan while the patient is on the table – including image acquisition, recontouring of the target and organs at risk, assessment of the plan with the contours of the day, and further planning as needed. 

The increased visibility and precision enabled by an MRI-guided system make it ideal for delivering stereotactic body radiotherapy (SBRT), which is a treatment technique in which a very high dose of radiation therapy is delivered in a few fractions (5 or fewer). When using SBRT targeting accuracy is an imperative, the target is frequently next to radiosensitive organs at risk. The capabilities of MRIdian for refining the target and reoptimizing the dose in real time while the patient is on the treatment table give us greater clinical confidence in delivering these higher ablative doses.

To date, we have completed approximately 45 patient treatments, and the number of patients treated per day is gradually increasing as MRI-guided radiotherapy becomes ingrained into our clinical practice. We’ve seen its value across a variety of indications including, breast, bladder, cervical, liver, pancreatic prostate, and rectal cancers. MRIdian has become our preferred method for treating complex cancer cases that are traditionally difficult to treat on a standard radiation therapy system due to the location of the tumor in relation to the surrounding soft tissue. MRIdian has allowed us to treat a number of patients who would not previously have been considered candidates for radiation therapy.

MRI-guided radiation therapy represents an exciting new frontier in radiation oncology. It is important that leaders in the field embrace these advances through the development of clinical trials, data collection, treatment policy, and protocols necessary to define the real benefits of this new technology. 

Radiation oncology has come a long way, and we have the opportunity to shape its future. The radiation oncologists on our team are proud to be part of the leaders who will write this page of history for the greater benefit of our cancer patients.

Editor’s note: This article first appeared in the Synergy Daily conference newspaper, available to attendees of the Synergy Miami interventional oncology meeting in November 2016. This article did not undergo peer review. 

Suggested citation. Portelance L. The Sylvester Comprehensive Cancer Center MRI-Guided Radiotherapy Program: The Next Frontier in Radiation Oncology. Articles from the official show daily for Synergy 2016. Intervent Oncol 360. 2017;6(1):E1-E3.

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