Scientists have found that combining exercise with chemotherapy may shrink tumours more than chemotherapy alone.
Researchers from the University of Pennsylvania found that exercise may benefit cancer patients undergoing chemotherapy.
Joseph Libonati, an associate professor in the School of Nursing and director of the Laboratory of Innovative and Translational Nursing Research, senior author on the study, and colleagues were 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 has is known to damage heart cells, which could lead to heart failure in the long-term.
"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," Libonati said.
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.
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.
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During the next two weeks, two of the groups received doxorubicin in two doses while the other two groups received placebo injections.
Mice in one of the treated groups and one of the placebo groups were put on exercise regimens, walking 45 minutes five days a week on mouse-sized treadmills, while the rest of the mice remained sedentary.
After the two-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 - 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 mice that both received chemotherapy and exercised had significantly smaller tumours after two weeks than mice that only received doxorubicin.
Further studies will investigate exactly how exercise enhances the effect of doxorubicin, but the team believes it could be in part because exercise increases blood flow to the tumour, bringing with it more of the drug in the bloodstream.
The study appears in the American Journal of Physiology.