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Exercise increases the number of immune cells in cancer patients

Scientists have long known that exercise decreases the risk of cancer, and reduces the side effects of cancer treatments while improving patients’ prognosis and quality of life. Now, two groundbreaking studies led by the University of Turku in Finland have found that even short bouts of light or moderate exercise can increase the number of immune cells in the bloodstream of cancer patients, some of which can be transferred to the tumor site and become active in destroying cancer cells.

“It was previously thought that cancer patients should just rest after a cancer diagnosis. Today, we have more and more researched information that exercise can even improve the prognosis of cancer. However, it is not yet fully known how exercise controls cancer,” said lead author of both studies Tiia Koivula, a research assistant at the Turku PET Center.

The studies involved 28 recently-diagnosed lymphoma and breast cancer patients who were asked to perform a 10-minute exercise on bicycle. 

“The pedaling resistance was determined individually for each patient so that it corresponded to light or moderate physical activity. The most important goal was that the patients were able to pedal for 10 minutes straight without exhaustion, but so that their heart rate increased,” Koivula explained.

The scientists collected blood samples once before and twice after the exercise, and compared the number of several different immune cells (known as white blood cells) in the samples taken before and after the exercise. 

The analysis revealed that, during the exercise, cytotoxic T cells and natural killer cells increased in the bloodstream of lymphoma patients, while in the breast cancer patients, the total number of white blood cells, as well as the number of intermediate monocytes and B cells also increased. Although these spikes in the number of immune cells were quick and transient, returning to a baseline level within 30 minutes after the exercise, the increase in cytotoxic immune cells looks particularly promising, since they are capable of destroying cancer cells.

The experts also found a link between the intensity of exercise and the increase in the number of immune cells in both patient groups. 

“Although our results indicate that the higher the exercise intensity is, the more immune cells are transferred from their storage organs into the bloodstream, it is notable that also light or moderate intensity exercise lasting for only 10 minutes will cause an increase in the number of immune cells which are important for fighting cancer,” Koivula said.

“Cancer treatments can make you tired and lower your motivation for exercise, which is why it is comforting to know that just 10 minutes of cycling or walking to a supermarket, for example, can be enough to boost the body’s immune system.”

However, further research is needed to clarify whether the newly generated immune cells are transported to the tumor after the exercise, where they could destroy cancer cells. Although this has already been shown to happen in preclinical studies, research in cancer patients remains incomplete.

The studies are published in the journals Frontiers in Physiology – Clinical and Translational Physiology and Nature Scientific Reports.

By Andrei Ionescu, Staff Writer

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