Cancer Featured Research

Behind the Research: A medical oncologist on tough-to-reach tumours and promising research

Dr. Rossana Pezo
Written by Dr. Rossanna Pezo

“The cancer has spread to your brain.”

These are difficult words for me to say, and difficult words for people to hear.

As a medical oncologist specializing in breast cancer, it’s a conversation I unfortunately have to have with many people each year. The brain is a common area for HER2+ breast cancer to spread. HER2+ means that the cancer cells contain this growth-producing protein.

There are not a lot of treatment options for patients whose breast cancer has spread to the brain. While there’s no cure, we try to manage the disease with radiation, surgery and drug therapies.

Drug therapies that work well to control cancer in other parts of the body don’t work as well in the brain, like Trastuzumab. This antibody therapy is a large molecule that has difficulty passing through the blood-brain barrier. This protective layer of cells around the brain prevents compounds circulating in the bloodstream from entering the brain but it also blocks potentially useful medications such as antibodies, chemotherapy drugs or other treatments for brain conditions.

So while Trastuzumab is really effective at treating cancer in the breast or that has metastasized to other areas, it cannot penetrate the brain easily. It’s frustrating: we know this therapy works well at controlling tumours, we just need to help it get it into the brain.

Soon after I started at Sunnybrook, I learned of research happening with focused ultrasound – using MRI-guided beams of ultrasound to temporarily open the blood-brain barrier. If the blood-brain barrier is opened, a drug like Trastuzumab could potentially more enter the brain more easily and target the tumour. It sounded like a unique way to approach the treatment of cancer that has spread to the brain. Therefore, I began working with Dr. Nir Lipsman and Dr. Maureen Trudeau, who were at the time setting up a trial to examine the safety of this approach for patients with breast cancer that has spread to the brain.

Our recently published study found that this approach is safe. The Trastuzumab was labelled so the research team could actually watch it pass through the blood-brain barrier and go into the brain. Patients were safe, and while these are early results, we saw some shrinkage in tumour size over time.

It feels amazing to be a part of something that’s a world-first and that shows so much potential. It’s a good first step in being able to offer patients with metastatic breast cancer another option for treatment. I’m excited to move into the next phase of this work and expand our trial to look more at how effective this treatment is at improving outcomes for patients with brain metastases.

To the patients involved in this and other clinical trials: Thank you. You put your faith and trust in the scientists, the physicians and the research teams who say “We are really excited about the promise of this treatment.” When it’s an early trial, you might be the very first person. You are so courageous for putting your hand up first. It’s through your courage that we can make life-saving breakthroughs.

Please talk to your doctor about taking part in clinical trials.

Read more: Sunnybrook researchers demonstrate groundbreaking evidence of focused ultrasound enhanced delivery of targeted antibody therapy to breast cancer that spread to the brain Learn more about focused ultrasound

About the author

Dr. Rossanna Pezo

Dr. Rossanna Pezo is a medical oncologist in the Odette Cancer Program at Sunnybrook Health Sciences Centre.