Combining exercise with chemotherapy shrunk tumors more than chemotherapy alone, according to research performed in a mouse model of melanoma.
Exercise has long been recommended to cancer patients for its physical and psychological benefits. This research team was particularly interested in testing whether exercise could protect against the negative cardiac-related side effects of the common cancer drug doxorubicin. Though effective at treating a variety of types of cancer, doxorubicin is known to damage heart cells, which could lead to heart failure in the long term.
The study was led by Joseph Libonati, PhD, FAHA, an associate professor in the School of Nursing and director of the Laboratory of Innovative and Translational Nursing Research at the University of Pennsylvania in Philadelphia. This research study was published in the American Journal of Physiology (2014; doi:10.1152/ajpregu.00082.2014).
“The immediate concern for these patients is, of course, the cancer, and they’ll do whatever it takes to get rid of it,” Libonati said. “But then when you get over that hump you have to deal with the long-term elevated risk of cardiovascular disease.”
Previous studies had shown that an exercise regime prior to receiving chemotherapy could protect heart cells from the toxic effects of doxorubicin, but few had looked to see whether an exercise regimen during chemotherapy could be beneficial.
To do so, Libonati’s team set up an experiment with four groups of mice. All were given an injection of melanoma cells in the scruffs of their neck. During the next 2 weeks, two of the groups received doxorubicin in two doses while the other two groups received placebo. The mice in one treated group and one placebo group were put on exercise regimens, walking 45 minutes 5 days a week on mouse-sized treadmills, while the rest of the mice remained sedentary.
After the 2-week trial, the researchers examined the animals’ hearts using echocardiogram and tissue analysis. As expected, doxorubicin was found to reduce the heart’s function and size and increased fibrosis, which is a damaging thickening of tissue. Mice that exercised were not protected from this damage.
“We looked, and the exercise didn’t do anything to the heart. It didn’t worsen it, it didn’t help it,” Libonati said. “But the tumor data—I find them actually amazing.”
The amazing result was that the mice that both received chemotherapy and exercised had significantly smaller tumors after 2 weeks than mice that only received doxorubicin. This could be partly because exercise increases blood flow to the tumor, bringing with it more of the drug in the bloodstream.
“If exercise helps in this way, you could potentially use a smaller dose of the drug and get fewer side effects,” Libonati said.
“People don’t take a drug and then sit down all day,” Libonati said. “Something as simple as moving affects how drugs are metabolized. We’re only just beginning to understand the complexities.”