An interdisciplinary team of clinicians and researchers from the Radiation Medicine Program at Princess Margaret Cancer Centre have created a unique facility aimed at developing for patients more precise, personalized cancer treatments with fewer side effects.
Combining extensive experience, expertise, teamwork and the high power of magnetic resonance imaging (MRI) with radiation into one space, is disrupting the radiation treatment landscape by adapting a treatment plan to a patient's "anatomy of the day" in real time.
"This technology is unprecedented and a milestone in advancing precision medicine in radiation," says Dr. Michael Milosevic, Director of Research, Radiation Medicine Program and Professor, Department of Radiation Oncology, University of Toronto. "We can reshape the dose based on the changes in size, shape and position of the tumour, while protecting more of the normal, surrounding tissue.
"This will help us reduce side effects and improve patient outcomes."
While the Princess Margaret and other institutions have used MRI machines and radiation treatment linear accelerators (Linac) separately for many years, this is the first time in the world that the combined technologies in one device have made it possible to see clearly the boundaries between tumours and organs, and observe how they move around during treatment.
The Elekta Unity MR-Linac is the latest generation of image-guided radiotherapy systems that make it possible to adapt the radiation dose in real time. As well, the MRI component produces detailed, 3-D images, with sharp contrast between the tumour and surrounding tissue. This decreases the risk of treating healthy tissue close to the cancer.
The Princess Margaret is one of two centres in Canada with this new technology, with the other being Sunnybrook Health Sciences Centre. In total, only 11 other sites in the world have the Unity MR-Linac.
"Organs are not rigid," says Dr. Daniel Letourneau, Head, Medical Physics, and Assistant Professor, Department of Radiation Oncology, University of Toronto, who has been involved in the MR-Linac project at the Princess Margaret since the beginning. "Tumours can be pushed aside by normal anatomy, depending on what's happening in the body. The bladder fills up, gas is passed through the intestines and rectum, and even breathing shifts tumours.
"These different types of movement have made it difficult previously to know where precisely a tumour is located during radiation treatment. But with real-time monitoring, we know where it is, and can adapt our treatment plans as the patient is lying in the machine."
A look at the journey of the new MR-Linac to the Princess Margaret Cancer Centre, one of only two sites in Canada with the new technology. There are only 11 others in use in the world. (Video: UHN)
Leading the world to develop MR-Linac liver protocols
To date, two prostate cancer patients have been treated in the new system at the Princess Margaret, and the program will begin treating liver cancer patients within the next few months.
The radiation program is part of the international Elekta MR-Linac Consortium, with more than 20 other institutions, which are all collecting data on imaging, treatment doses, tumour control, tissue toxicity and quality of life of patients.
The Princess Margaret will be leading the Consortium's liver tumour site group in developing protocols and approaches to treating liver cancer with the MR-Linac.
"The liver and tumour move when you breathe, but sometimes each does not move in the same way," explains Colleen Dickie, Director, Operations and Assistant Professor, Department of Radiation Oncology, University of Toronto. "It is a dynamic, constantly changing environment.
"Surrounding organs expand and contract, changing the shape of the liver. The liver is very tricky to treat because of this movement and its sensitivity to radiation."
A global leader in MRI-guided radiation treatment
The Princess Margaret has a long and rich history in developing innovative MRI-guided technologies and treatment approaches. The aim is to develop more precise, personalized treatments to cure more patients with fewer side effects.
One way to do this is adapt treatment to the often rapidly changing course of a patient's cancer. The program's Adaptive Radiation Oncology approach wants to ensure that that every patient gets the right treatment at the right time.
Putting this into practice, a few years ago, the program developed another facility where an MR scanner could move on ceiling-mounted rails between a radiation treatment machine (Linac) and a brachytherapy-enabled surgical suite for the delivery of highly precise MRI-guided cancer treatment.
That suite allows patients to be scanned and treated in one spot rather than having to visit several locations in the hospital.
"It's the precision of the imaging and how closely it is integrated with the treatment that gives us new information about how tumours change with time and during treatment," emphasizes Dr. Milosevic.
These technologies, along with the clinical and technical expertise of the radiation team, enabled them to take on the latest challenge of creating a suite for the MR-Linac – one of the longest design projects in the program.
Collaboration leads to seamless first treatment
"We have a lot of history in understanding how the worlds of imaging and radiation treatment come together," says Colleen, noting that MRI and radiation are traditionally incompatible since MRIs use strong magnets in their imaging process that attract metal.
"We are proud of our MR-guided program, and we were able to build on our extensive knowledge to implement this latest addition to create a seamless and successful experience for our first patients," she notes.
She adds that more than 50 staff from the Radiation Medicine Program were involved in the planning, design and construction of the space for the MR-Linac, along with the installation of the equipment and the treatment of the first patient. The project took more than two years from initial planning to clinical implementation.
Dr. Andrew Bayley, radiation oncologist who was involved in the preparations and in treating the first patients, emphasized the strong teamwork from many disciplines and the meticulous practice sessions involving hundreds of radiation plans carefully honed over more than six months.
The plans were further fine-tuned by using healthy volunteers to undergo scanning, without radiation, on the MR-Linac. Even the first patient had a trial run so that everyone was well-prepared.
In fact, the first patient received a new personalized plan every day of his treatment, a plan that was adapted to his anatomy before receiving treatment. This is now the new standard of care for this machine.
"We hope that because we can personalize each treatment with the improved MR imaging, while protecting normal structures, we will be able to have higher cures with less risk of toxicity," says Dr. Bayley, who is also an Assistant Professor, Department of Radiation Oncology, University of Toronto. "We are now thinking of new ways to use radiation more effectively to increase cure rates with fewer patient visits to the cancer centre."
Special attention was paid to create an exceptional patient experience, as part of the MR-Linac suite design. A private patient education area with lockers and change rooms were important parts of the design to create a pleasing environment for patients and their families.
To enhance the best team-based approach, a collaborative space was created in the suite for the multidisciplinary staff to work together and discuss treatment plans for the patient.
Future plans
With the radiation team currently focusing on patient and tumour anatomy, the next phase is to get information from the scans about tumour biology and treatment response.
This can be used to guide individual patient treatment as we begin to better characterize individual tumours in each patient, adds Dr. Letourneau, by learning how to rapidly extract key biological information from the tumours to allow even greater real-time treatment adaption.
