Doctor with deadly tumour helps test new treatment
Sunnybrook brain cancer trial program combines radiation with advanced MRI
After a little lapse in memory he experienced in the second week of February, Dr. Jim Swan instantly thought of his identical twin brother George, who had died of a brain tumour a few months earlier.
And just as quickly, the longtime St. Michael’s Hospital cardiologist diagnosed himself with the same disease.
“I guess I did, I guess I did. I’m an old doctor,” Swan says, both pride and resignation evident in his voice.
Scans and a biopsy would confirm that, like his brother, the 74-year-old had developed a glioblastoma multiforme tumour, or GBM — a cruel growth, relentless in its malevolence, that defies most standard treatments.
But Swan may be helping to loosen that defiance.
He was instrumental in setting up a $3-million fund at the University of Toronto to help search for any genetic components to the disease, which has rarely occurred in both identical twins in the past.
More immediately, however, he has undergone an experimental treatment at Toronto’s Sunnybrook Health Sciences Centre that may prove to be the biggest breakthrough in the disease in decades.
Known as MR-Linac, the treatment is derived from a device that, for the first time, combines radiation therapy with a high-powered magnetic resonance imaging capacity.
That pairing allows the MRI (the MR in the name) to detect changes in a tumour and direct the linear accelerator (the Linac) radiation beam to the most dangerous parts as it shifts and morphs, often on a daily basis.
“So we can start using advanced MRI to help guide our ability to target the tumour,” says Dr. Arjun Sahgal, who’s leading the Sunnybrook arm of the international project.
Sahgal notes that little progress has been made in curing or slowing the ailment for at least 15 years.
In the past, physics had been the biggest obstacle to the targeting combination. What results is the magnetic fields of the MRI wreak havoc with the highpowered electron stream that delivers the therapeutic radiation.
But through some software advances, the machine, now known as the Elekta Unity MR-Linac, allows the beam to pierce through its magnetic elements. That magnetic resonance creates a map that the radiation stream follows.
Sunnybrook is one of seven international centres to initially receive a device. And although all seven have been using it on several different cancer types, each is concentrating on a specific form of the disease in the initial calibration phase, during which the machine is being prepared for coming clinical trials.
The Sunnybrook team is specializing in glioblastomas, the most common and deadly form of brain tumour and the type that killed The Tragically Hip frontman Gord Downie in 2017.
If the trials — set to begin within six months — prove successful, MR-Linac could revolutionize treatment of the disease, says Dr. Hany Soliman, a radiation oncologist at Sunnybrook.
Standard treatment for glioblastomas currently includes the trio of surgery, chemotherapy and radiation. But surgery is a relatively crude device to use in the brain, with some cancer always remaining at the tumour’s margins, Soliman says.
And the drugs that have been brought to bear on the disease have so far failed to nudge survival or remission rates up significantly.
“So our mission is to use advanced radiation technology to try and improve outcomes, not only for improving control of the tumour (but for) less side effects,” Sahgal says.
“We’re just better able to adapt the radiation to the tumour.”
DR. ARJUN SAHGAL SUNNYBROOK MR-LINAC LEAD
Historically, radiation of glioblastomas has involved one MRI before the first daily bout to locate the tumour and aim the beam. After that hard-to-book MRI, there would be six weeks of active radiation; and then a second MRI scan another month later to see how it did, he says.
“We go through weeks of radiation treatment without really knowing exactly what’s happening during the treatment,” says Soliman. “So we’re a little bit blind, I mean that’s a fair word to say, during the course of your radiation treatment.”
That will all change with the MR-Linac technology, Sahgal says.
“Now we’re doing MRIs every single day — instead of three months later — we’re tracking it, we’re visualizing it,” says Sahgal, a world leader in brain and spinal tumours.
And about 20 to 30 per cent of the time, he says, the MR-Linac is seeing changes in the stealthy cancer that will cause doctors to change medication or radiation treatments, he says.
“We’re just better able to adapt the radiation to the tumour,” Sahgal says. “Sometimes it gets bigger, sometimes it’s getting smaller and sometimes it’s morphing, and what we do is change the radiation map.”
Indeed, the radiation targeting — which is so important to ensure that the cancer is killed while normal brain tissue is preserved — can be changed virtually in real time.
“So this is what I really call opening your eyes,” Sahgal says. “No MRI (scan) for three months to an MRI every single day.”
In some cases, Sunnybrook doctors have seen tumour growth in patients so pronounced during the radiation period that further surgery was needed. When tumours are seen to shrink, on the other hand, radiation doses can be lowered, lessening their toxic effect on normal brain tissues.
So far, the Sunnybrook team has treated about 80 glioblastoma patients, with a keen eye on fine-tuning the technology. That’s far too few cases to pass any judgments on the technology’s therapeutic effectiveness. Those kinds of results will have to await clinical trials.
That initial study, Sahgal says, will focus on reducing the amount of brain tissue that has to be radiated while still controlling the glioblastoma tumour.
“Our hypothesis is the toxicity will be less and our outcomes will be better,” Sahgal says.
Swan, the patient, says he felt an obligation as a physician to be part of a potential medical advancement when asked.
“It’s new, and I said sure,” says Swan, whose wellwishers as cardiologist to the NHL’s oldimers hockey team have included hockey greats Frank Mahovlich, Bobby Baun and Ken Dryden since his diagnosis. “You want to try and do nice things for people,” and help the Sunnybrook team make progress.
A pioneer in cardiac scanning, Swan would like to see the kind of vast progress in brain tumours that have been realized in his field since he started practising in 1977.
With the international MR-Linac consortium now nearing clinical trials in many areas of cancer, Sahgal is cautiously optimistic that will happen.
“Ultimately our mission is to prove safer treatment … with better ability (for) tumour control with less toxicity,” says Sahgal. “And that’s the holy grail we’re embarking on to prove. We’re not there yet, but we’re getting there as a global community. This will likely be the standard of care in the future.”