When less radiation means better results

TORONTO – Dr. Andrew Loblaw (pictured), a radiation oncologist at Sunnybrook Health Sciences, and his colleague Dr. Patrick Cheung have spent decades researching and perfecting SABR – stereotactic ablative body radiotherapy – a high-precision, external beam radiation treatment.

In 2018, Sunnybrook became the first hospital in Canada to change treatment protocols for most men with intermediate risk prostate cancer. Traditionally, radiation treatment plans involved visits to the cancer centre five days a week for eight weeks.

“With SABR, we’ve reduced that to once per week, for five weeks, and we are really proud of that change,” Dr. Loblaw says.

The SABR treatment involves implanting tiny markers made of gold into a prostate tumour and using image-guidance to precisely target the tumour with radiation from outside the body. It is done on a regular linear accelerator, which is the standard equipment used for external beam radiation. That means any cancer centre providing radiation treatment could adopt SABR, Dr. Loblaw says.

“Because of the precision, we are actually able to deliver less radiation into the body, which is better for patients too,” he says.

The new SABR treatment plans were years in the making.

“We were always taught that the best way to treat prostate cancer was with six to eight weeks of low-dose treatments. Then about 20 years ago, some scientists in the United States noticed that prostate cells were more easily killed with high dose per day radiation,” Dr. Loblaw says. “So we used that theory to start developing this technique – delivering fewer radiation treatments to a tumour, but ultimately packing a greater punch.”

Because prostate cancer is often a slow-growing cancer, researchers had to watch and check in on patients for years to ensure the SABR was working effectively.

And, since the side effects of radiation treatments can take years to surface, it was important for the researchers to track patients over time to ensure the treatments were also safe. In fact, the first cohort of patients was followed for a minimum of 11 years.

“This kind of work takes a long time to fund and to complete,” Dr. Loblaw says. “But ultimately, we’ve found that SABR is highly effective for treating prostate cancer, it’s well tolerated by patients – meaning there are few side effects – and it’s very convenient for patients.”

Now, Dr. Loblaw and his team are going even further in their SABR research.

“We are looking into whether we can effectively treat some prostate patients with just one dose of radiation,” he says.