Study Explores Exercise’s Role in Boosting Tumor-Killing Cells in Breast Cancer Patients

A recent study from the University of Turku, Finland, suggests that a mere 30-minute exercise session can significantly enhance the proportion of tumor-killing white blood cells in the bloodstream of breast cancer patients.

White blood cells are integral to our immune system, combating cancer, bacteria, and viruses. However, according to the study’s authors, not all white blood cells are equal in their fight against cancer. They explained that cytotoxic T cells and natural killer cells are the primary cancer-destroying cells, while regulatory T cells and myeloid-derived suppressor cells can actually promote cancer growth.

"The balance of different types of white blood cells determines whether the immune system works to destroy cancer or to support it," explained Doctoral Researcher Tiia Koivula from the University of Turku. "If there are more cancer-destroying cells than cancer-promoting cells in the tumor area, the body is more capable of fighting cancer."

The study involved twenty newly diagnosed breast cancer patients who had not yet commenced treatment. Participants cycled on a bicycle ergometer for 30 minutes at a self-selected resistance level. Blood samples were collected at rest before the exercise, during the exercise, and after the exercise to assess the various types of white blood cells.

The findings revealed that several types of white blood cells increased during exercise, particularly cytotoxic T cells and natural killer cells. Conversely, the number of cancer-promoting regulatory T cells and myeloid-derived suppressor cells remained unchanged. The researchers also found that the proportion of natural killer cells increased significantly relative to the total white blood cell count, while the proportion of myeloid-derived suppressor cells decreased.

"We found that during exercise, the number and proportion of cancer-destroying cells increase in the bloodstream, while the proportion of cancer-promoting cells either stays the same or decreases," Koivula noted. "However, it is still unclear whether these changes in the bloodstream also lead to changes in the white blood cell counts in the tumor area."

The study observed that the levels of almost all white blood cell types returned to resting values one hour after exercise. While the destination of these cells post-exercise remains unknown, preclinical studies suggest that cancer-destroying cells might migrate into the tumor area.

Further analysis indicated that the response of white blood cells to exercise might vary depending on the type of breast cancer. Larger tumors were associated with a smaller increase in natural killer cells, and estrogen and/or progesterone receptor-positive breast cancers saw a lesser increase in cytotoxic T cells compared to hormone receptor-negative cancers.

"In our previous study, we found small indications that the type of breast cancer might affect the effects of exercise on white blood cells," Koivula said. "However, the correlations we found were not very strong, and therefore, no decisive conclusions can be drawn from the results. According to current knowledge, it is beneficial for all cancer patients to exercise, and our recent study supports this notion."