TORONTO - Canadian researchers have developed a fibre-optic probe they believe could help neurosurgeons track down stray cancer cells in patients with invasive brain tumours, thereby potentially reducing the risk of recurrence and improving life expectancy.
The hand-held device, called a Raman spectroscopy probe, was developed by researchers at McGill University for use by neurosurgeons in the removal of brain tumours called gliomas, which typically infiltrate healthy brain tissue.
The difficulty for surgeons is that current imaging technologies like MRI are unable to detect all the malignant cells that have seeded themselves within normal tissue outside the solid tumour, said Dr. Kevin Petrecca, the chief of neurosurgery at the Montreal Neurological Institute who helped design and test the probe.
"So being able to visualize the tumour in its entirety is one area we're unsuccessful at and the second one is that even if you could visualize the entirety of the tumour, it doesn't mean that you could remove all of those areas," Petrecca, who performs hundreds of brain tumour surgeries each year, said from Montreal.
"As a glioma surgeon, that's all I think about every day: I wish I could see those cells."
By using Raman spectroscopy — a technique that measures the way an object’s molecules scatter light — Petrecca said neurosurgeons can pinpoint cancer cells in small spots about a millimetre deep where the probe comes in contact with brain tissue.
In a study published Wednesday in Science Translational Medicine, the researchers showed the device detected not only the dense tumour mass, but also individual cancer cells that had penetrated surrounding tissue in 17 patients with advanced gliomas.
Since then, researchers have used the probe on a total of 40 patients without adverse effects. The team is planning a follow-up clinical trial that will assess whether use of the device increases patient survival.
Petrecca said the beauty of the probe is its simplicity: results from the probe are shown on a laptop within a second of it contacting the targeted area, allowing the surgeon to remove a tiny section of brain tissue if it is unlikely to cause physical or cognitive impairments in the patient.
Minimizing the amount of residual cancer left after surgery can affect survival, he said.
"The better resection you can do, the longer the patient lives. We're really talking about the difference of living six months versus three, four, five, six years. So it's a big, big deal."
There are different types of gliomas: some are more invasive and aggressive than others, usually strike at different points in life, and have varied life expectancies that range from months to decades, depending on the tumour type and at what stage it is diagnosed.
Petrecca believes that with further development, the Raman-based probe could become a valuable tool in the operating room, with a cost that's a tiny fraction of equipment like intraoperative MRIs and surgical robots.
"So do I think it's going to be transformational? Absolutely."
Dr. Mark Bernstein, a neurosurgeon at Toronto Western Hospital who specializes in brain tumours, called the Raman-based probe "an innovative application of sophisticated scientific theory and technology."
However, he said it would be impossible to identify every cancer cell. And even if it were possible, surgically chasing down all the cells could end up destroying vital brain tissue, potentially leaving the patient unable to speak, walk or see.
The tumour also might still recur because the genetic underpinnings that initially gave rise to the cancer still remain, said Bernstein, who was not involved in the research.
"I truly applaud the authors' idea and excellent and careful study of it, and await further data and advancement in techniques. But the chance of this technology translating into improved outcomes for patients with primary brain tumours is very low in my opinion," he said.
In fact, Bernstein believes that if a cure for these brain tumours is ever found, the solution won't be surgical but pharmaceutical, in the form of drugs that target the cancer cells at the molecular level while leaving healthy neurons unharmed.
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