The Evolution of Radiation in the Treatment of Brain Tumours
By Dr. Arjun Sahgal, 2018 Brain Tumour National Conference Keynote Speaker
Although one of the most effective treatments for several kinds of brain tumours, radiation is also associated with long-term side effects. In the past, it was hard to map out where exactly to deliver the radiation, and that led to disabling side-effects like difficulty thinking clearly, problems with memory, seizures, personality changes and some permanent organ dysfunction, depending on where the tumour was in the brain.
Over the years, radiation technology has undergone several transformations with the advent of magnetic resonance imaging (MRI), software and hardware that allows us to plan radiation more accurately around targets seen on the MRI, and image-guidance to allow for high-precision delivery.
These developments in mainstream linear accelerators — the machines that deliver the radiation — has resulted in dramatic reductions in the amount of normal brain tissue hit with radiation and made it possible to deliver higher doses than could otherwise be achievable with the radiation technology of the past. Furthermore, specialized units have been developed that allow for just single-day sessions of radiation for small non-malignant tumours (like meningiomas and acoustic neuromas) and brain metastases. Technology like the Gamma Knife®, CyberKnife® and modified linear accelerators has resulted in better access for Canadians to this form of treatment, known as stereotactic radiosurgery — using focussed beams of radiation to hit the tumours.
One of the latest technical developments in the field of radiosurgery is the Gamma Knife® Icon, and the first patient in Canada was treated at Sunnybrook Health Sciences Centre in 2017 using this frameless high-precision radiosurgery technology. The Gamma Knife® Icon allows us treat 10 or even 20 brain metastases in a single day, using a mask for stability rather than a head frame drilled to the forehead. This type of radiosurgery means less use of whole brain radiation, and better quality of life for our patients.
Most recently, at Sunnybrook Health Sciences Centre, we have made a major investment and installed the first MR-Linac in Canada. This new technology marries a high-field strength MRI with a linear accelerator and will let us target tumours and monitor their response to radiation with unprecedented precision – even as a tumour moves inside the body – thanks to the machine’s real-time MRI guidance.
Sunnybrook Health Sciences Centre is one of the founding members of a seven-member international consortium that is testing and refining the MR-Linac and preparing the machine for the first clinical trials. Clinical trials will begin at Sunnybrook Health Sciences Centre once Health Canada approval is received, a process that is underway. Sunnybrook Health Sciences Centre is the Brain Site Lead in this consortium, and our team has been tasked with determining the best possible ways to use this technology to treat brain tumours. For example, we have been developing ways to determine the biology of the tumour as it is being treated, and we have found ways to see resistance and response early on into the 6-week course of radiation for glioma. Eventually this research will allow us to figure out a strategy to make the treatment more effective and safer as we personalize radiation treatments for patients with brain tumours.
The next decade of research and clinical radiation delivery promises to be exciting and meaningful for patients as we strive to improve outcomes for patients with brain tumours. Learn more about emerging technology in the field of radiation from Dr. Sahgal at the 2018 National Brain Tumour Conference in Toronto October 19- 20.
Dr. Sahgal is the Professor of Radiation Oncology and Surgery, University of Toronto Deputy Chief, Department of Radiation Oncology, Odette Cancer Centre Sunnybrook Health Sciences Centre. He is an international clinical and research leader in the field of high precision stereotactic radiation to the brain and spine for both metastases and primary tumours.