Regular exercise is already known to protect the heart, strengthen muscles and improve overall health. New research suggests it may also help the immune system fight lung cancer, especially in people carrying excess body fat.
Scientists at Roswell Park Comprehensive Cancer Center found that obesity can change immune activity inside the lungs in ways that make it easier for tumors to grow. Exercise appeared to reverse some of these harmful changes and was linked to slower tumor growth in laboratory animals.
The study was published in the Annals of Surgery. It was led by researchers including Dr. Sai Yendamuri, chair of the Department of Thoracic Surgery at Roswell Park, and Andrew Ray, an associate professor of oncology in the Department of Cancer Prevention & Control.
Lung cancer remains one of the world’s deadliest cancers. Non-small cell lung cancer, or NSCLC, is the most common type and accounts for the great majority of lung cancer cases.
The immune system normally has cells that can recognize and attack abnormal cells before they become dangerous. Cancer, however, can create an environment around a tumor that weakens these defenses and allows malignant cells to survive.
Obesity may make this problem worse. Excess body fat is not simply stored energy; fat tissue can release chemical signals that influence inflammation, metabolism and the behavior of immune cells throughout the body.
The Roswell Park team wanted to know whether physical activity could change this immune environment. They first studied both lean and obese mice, including healthy animals and mice with non-small cell lung cancer.
Some animals were able to run on an exercise wheel, while others remained inactive. The researchers then examined the tumors and immune cells in the lungs to see how obesity and exercise changed the body’s response to cancer.
They used advanced laboratory methods to measure which genes were active and to identify different types of immune cells. The researchers were particularly interested in cells that either help attack tumors or reduce the immune system’s ability to fight them.
One important group was regulatory T cells, often called Tregs. These cells normally perform a useful job by preventing the immune system from becoming overactive, but inside a tumor they can sometimes suppress the immune attack that doctors want against cancer.
The team also studied CD8 T cells. These immune cells can directly recognize and kill cancer cells, making them an important part of the body’s natural defense against tumors and of the response to some modern cancer treatments.
Among obese mice, exercise was associated with fewer tumor-protecting regulatory T cells and more CD8 T cells. This pattern was seen in obese animals with and without lung cancer, suggesting that physical activity changed the immune environment of the lungs.
Most importantly, tumors grew more slowly in mice with lung cancer that exercised. This suggests that the immune changes were not simply interesting laboratory findings but may have had a real effect on how quickly the cancer developed.
The researchers then looked for similar patterns in people. They examined lung cell samples from 73 patients with non-small cell lung cancer and compared the results with information about body fat and physical activity.
Samples from patients who exercised contained fewer regulatory T cells. They also had fewer fat-related myeloid cells, another group of immune cells that can interfere with the body’s ability to attack a tumor.
These human findings support the idea that exercise may create a more favorable immune environment around lung cancer. However, they do not prove that exercise alone slows tumor growth or improves survival in patients.
The study has several important limits. Much of the direct evidence that exercise slowed cancer growth came from mice, and biological effects seen in animals do not always produce the same results in humans.
The human part of the study was also observational, meaning patients were not randomly assigned to exercise or remain inactive. People who exercise may differ from inactive patients in many other ways, including general health, smoking history, diet and ability to tolerate physical activity.
Still, the study offers a useful explanation for how exercise might support cancer treatment. Rather than acting directly like a cancer drug, physical activity may help reshape the immune system so that tumor-killing cells can work more effectively.
Andrew Ray said exercise could potentially serve as a free and noninvasive addition to a patient’s treatment plan. That does not mean exercise should replace surgery, radiation, chemotherapy, targeted drugs or immunotherapy.
For people with lung cancer, the safest amount and type of activity can vary greatly depending on the stage of disease, treatment side effects and overall fitness. Patients should discuss exercise with their cancer care team, especially if they have breathing difficulties, severe fatigue or other medical problems.
Overall, the findings are promising because they connect obesity, exercise and cancer immunity in a clear biological pathway. Larger human trials are now needed to determine whether structured exercise can actually improve treatment response, reduce cancer progression or help patients live longer.
If you care about cancer, please read studies that artificial sweeteners are linked to higher cancer risk, and how drinking milk affects risks of heart disease and cancer.
For more health information, please see recent studies about the best time to take vitamins to prevent heart disease, and results showing vitamin D supplements strongly reduces cancer death.
Source: Roswell Park Comprehensive Cancer Center.
