For a decade, the approach to radiation oncology in Canada has been shifting toward a more precise, less invasive model. At the center of this evolution is the Cancer Ablation Therapy (CAT) program at Sunnybrook, which has grown from an ambitious vision to eliminate the surgical footprint for specific cancers into the nation’s largest radiotherapy program.
Launched in 2016 within the Odette Cancer Program, the initiative was designed to move beyond traditional “one-size-fits-all” radiation. By integrating a specific trio of advanced technologies—the Gamma Knife Icon, the MR-Linac, and an MR-Guided Brachytherapy suite—the program allows clinicians to target tumors with extreme accuracy although sparing the surrounding healthy tissue. This level of precision is critical in reducing the systemic trauma often associated with cancer treatment.
The impact of these tools is most evident in the clinical outcomes for patients with complex malignancies. For those facing brain tumors, the Gamma Knife has enabled advanced stereotactic radiosurgery for patients with up to 50 distinct tumors. Similarly, the MR-Linac has been used to reduce the number of required stereotactic body radiotherapy sessions for prostate cancer, effectively lowering the number of hospital visits and reducing the burden on the patient’s daily life.
The Path to Adaptive Radiation Therapy
The program’s trajectory has been defined by a willingness to embrace “first-in-country” technology. A pivotal moment occurred when Sunnybrook became the only Canadian member of the MR-Linac Consortium. This partnership required years of rigorous planning and construction, culminating in August 2019 when the team performed the first clinical treatment on a patient with glioblastoma using the MR-Linac in Canada.
Dr. Arjun Sahgal, Chief of Radiation Oncology, identifies the installation of the MR-Linac as one of the program’s most significant milestones. The ability to see the tumor in real-time via MRI while delivering radiation allows for a level of adaptability that was previously impossible. This shift is not merely technical. We see deeply human. For patients with cervical cancer, advancements in MRI-Guided Brachytherapy have shortened treatment times so significantly that many can avoid hospital admission entirely, transforming a grueling process into a more humane, outpatient experience.
This commitment to refining the patient experience is mirrored in the program’s research. Sunnybrook has led several international clinical trials focusing on pancreatic, liver, brain, and prostate cancers. These trials are aimed at redefining the standard of care—specifically by reducing the number of treatment fractions required without compromising the clinical outcome.
Transitioning to CA(A)T: The AI Era
In 2025, the program underwent a strategic rebranding to become the Cancer Ablation Adaptive Therapy (CA(A)T) program. The addition of the “Adaptive” element signals a shift toward real-time therapy adjustments. Rather than following a static plan created at the start of treatment, clinicians can now evaluate how a tumor is responding and modify the radiation dose or target on the fly.
Lori Holden, the Strategic Lead for Sunnybrook’s Radiation Therapy Program, explains the shift: “As we continue to innovate, we’re expanding our treatment capabilities with new machines incorporating advanced AI technologies that will allow for responsive and adaptive treatment. This means we will be able to adjust a patient’s therapy in real time—pausing, assessing how the tumour is responding, and tailoring the treatment to target it more effectively rather than waiting months to evaluate the results.”
This new phase of adaptive radiation therapy is supported by three primary technological pillars:
- AI-Driven Planning: The adoption of the RayStation platform has reduced treatment planning timelines from several days to mere minutes.
- Daily CT Integration: The Ethos HyperSight system allows for adaptive adjustments based on daily CT imaging, providing a flexible alternative when MRI guidance is not required.
- Continuous Motion Management (CMM): An update to the MR-Linac specifically targets “moving” targets—tumors in the lungs, kidneys, pancreas, and prostate that shift with the patient’s breathing or organ movement.
Program Evolution Timeline
| Year | Milestone | Impact |
|---|---|---|
| 2016 | CAT Program Launch | Establishment of Canada’s first dedicated CAT program. |
| 2019 | First MR-Linac Treatment | First glioblastoma treatment using MR-Linac in Canada. |
| 2025 | Rebrand to CA(A)T | Shift toward AI-driven adaptive and personalized therapy. |
| 2026 | CMM Update | New paradigms for treating “moving” targets in the lungs and pancreas. |
The Future of Personalized Oncology
The overarching goal of the CA(A)T program remains consistent with its 2016 inception: to maximize the precision of radiation while minimizing side effects and preserving the patient’s quality of life. This progress is fueled by a combination of philanthropic support and deep collaboration with global research partners.
As the program moves into its second decade, the focus is on the integration of artificial intelligence to move oncology from a reactive model to a responsive one. By leveraging tools like the Ethos HyperSight and continuous motion management, the team is working toward a future where radiation is as dynamic as the diseases it treats.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Patients should consult with their own healthcare provider for personalized treatment plans.
The next phase of the program involves the full rollout of continuous motion management updates to expand treatment options for pancreatic and lung cancer patients. We invite you to share your thoughts on the role of AI in healthcare in the comments below.
