A new scanner at Edmonton’s Cross Cancer Institute is allowing doctors and researchers to see cancers like never before, with the potential to provide the most detailed images to-date of what cancer looks like and how it is working in the body.
Dr. Sandy McEwan, a professor in the Department of Oncology at the Cross, started using the PET-MRI scanner this past May. The scanner blends PET (positron-emission tomography) with MRI (magnetic resonance imaging). According to McEwan, the result is “exquisite pictures of structure” from the MRI, combined with the ability to see and measure actual metabolic processes through PET.
“Our ultimate goal is to use this technology to improve patient selection for treatment,” says McEwan. “It’s the idea of precision medicine: treating the right patients, at the right time, with the right dose and the right drug.”
Prior to the arrival of the PET-MRI imaging scanner, the Cross Cancer Institute relied on a blended PET-CT scanner, which remains in routine clinical use and continues to be an extremely valuable clinical tool. The CT (computed tomography) scan works well to show a 3D X-ray image, including any abnormalities in structure and blood flow. But MR imaging produces a much more detailed image in most cases.
Typically, for the PET portion of the scan, a radio-labelled glucose marker is injected into the patient. Cancer uses more glucose than normal tissue does, so the injected marker will show the cancer and how aggressive it is, with a more aggressive cancer using more glucose. Researchers can also use different tracers in the PET-MRI when they want to see how another body structure, for example the brain or heart, is working.
When the MR images are combined with the PET, a 20- to 40-minute scan can show doctors both the anatomy and function of a cancer — not only what a tumour looks like, but also what it is doing in the body. Doctors can use this information to predict treatment outcomes, including what kind of drugs might be able to get into a cell, how the tumour might grow and whether there is oxygen in a tumour.
“The absence of oxygen will probably mean that the cancer will not respond to many current [available] treatments,” explains McEwan.
Initially, the PET-MRI will be used for research. “Cancers in the pelvis and the brain will be the ones that will benefit the most and where routine clinical use is most likely,” says McEwan. One project will look at how to create better radiation plans for prostate cancer treatment. A second will look at rare neuroendocrine (gut and pancreatic) cancers and whether they will respond to newly available drugs.
The Cross Cancer Institute PET-MRI is a provincial resource, with patients from all parts of the province involved in research and, eventually, clinical scans. “We think that it will very quickly become a routine tool for some cancers,” says McEwan. Another exciting application for the PET-MRI is to examine the toxicity effects of chemotherapy. Researchers hope to see why some patients experience side effects like extreme fatigue from chemotherapy treatments, while other patients have much less severe symptoms.
“This is the outcome of a 19-year collaboration,” McEwan says. “Nineteen years ago, we made our first CFI application to put in a PET scanner at the Cross. The Alberta Cancer Foundation has supported us through thick and thin in maintaining the PET facility, not only as a clinical program, but also supporting PET clinical research and expanding it through the acquisition of the PET-MRI. This is a long-standing partnership that continues to give back to the people of Alberta and continues to support cancer services in Alberta.”