Physical activity may slow cancer growth: Montreal study

Proteins produced by muscles during physical activity could inhibit the development of prostate cancer cells and thus slow the progression of the disease, suggests a study involving a Montreal researcher.

The same phenomenon could apply to other types of cancer, said Dr. Fred Saad, who heads the urology department at the Centre hospitalier de l'Université de Montréal.

"Everything suggests that this is not at all unique to prostate cancer," he said.

Saad and his colleagues at Australia's Edith Cowan University recruited nine patients with a very advanced and aggressive form of prostate cancer and asked them to undergo 34 minutes of intense training on a stationary bike.

Blood samples taken before and after the exercise session revealed to the researchers that the subjects' blood contained elevated levels of myokines, proteins that are produced by skeletal muscles, after the workout.

When these myokines were exposed to prostate cancer cells in the laboratory, the growth of the cells was reduced by about 17 per cent.

Blood levels of myokines and anti-cancer activity returned to normal after 30 minutes.

"We've identified things in the blood that are actually anti-cancerous," Saad said. "So, beyond all the quality of life, beyond all the things we thought we understood, we're starting to find that it almost acts like an anti-cancer drug. And that's really fascinating."

The findings of this study are in line with other work Saad has previously been involved in, which seemed to show that prostate cancer can progress less quickly in patients who exercise and are physically fit.

In other words, he says, being physically fit probably maximizes the chances of preventing a prostate cancer that is currently just being monitored from developing into a disease that needs to be treated more aggressively.

"And if treatment ever becomes necessary," says Saad, "patients who are fit will be better able to tolerate it."

"It's not easy to tolerate chemotherapy, it's not easy to tolerate certain treatments, and patients who are really out of shape, unfortunately, often don't get the maximum amount of treatment because they're out of shape," he said.

The optimal dose of exercise to fight cancer is stil unclear. However, one of the Australian authors of the study, Professor Rob Newton, said in a statement that it probably takes at least 20 minutes a day, incorporating resistance exercise to build muscle and stimulate myokine production, to maintain a "chemical environment" in the body that is conducive to cancer suppression.

Prostate cancer patients, Saad concluded, are mainly older men who were not used to staying fit. So it may be that the benefits of physical activity are partly due to the fact that they are starting from further back. It should now be tested whether myokines have the same effect on the cancer of a 25-year-old who is already in good shape.

The findings were published in the medical journal Prostate Cancer and Prostatic Diseases.

- This report by The Canadian Press was first published in French on Dec. 21, 2022