Many doctors recommend exercise to their cancer patients if only for its psychological perks, yet a new study finds exercise may produce a substantial added benefit for cancer patients who are undergoing chemotherapy. Using an animal model of melanoma, the researchers found that combining exercise with chemotherapy shrunk tumors more than chemotherapy alone. “If exercise helps in this way, you could potentially use a smaller dose of the drug and get fewer side effects,” said Dr. Joseph Libonati, an associate professor at University of Pennsylvania and senior author of the study.

Happy Accidents

Many a scientist has discovered something important while searching for something else entirely. For instance, while studying the vaginal smears of animals and women throughout their sex cycles, Dr. George Papanicolaou was amazed to find he could easily see abnormal cancer cells under his microscope. From this happy accident, he developed the “Pap Smear.”

Similarly, for the current study, Libonati and his colleagues were testing whether exercise could protect against the heart-related side effects of doxorubicin, a drug used to treat a range of cancers, including bladder, liver, lung, prostate, thyroid, and some types of leukemia. Though effective, doxorubicin is known to damage heart cells, which may lead to heart failure in the long-term. With previous studies showing exercise prior to receiving the drug could protect heart cells, none or few studies had investigated whether an exercise regimen during chemotherapy might be beneficial.

And so Libonati and his team set to work. They designed an experiment with four separate groups of mice. After giving all of the mice an injection of melanoma cells in their necks, only two of the groups received doses of doxorubicin, while the other two groups received placebo injections. Then, mice in one of the chemo groups and mice in one of the placebo groups began their exercise regimens, walking 45 minutes, five days a week, on mouse-sized treadmills — this must be one memorable sight — while the other mice remained sedentary. Upon conclusion of the trial, the researchers examined the animals’ hearts and found, as expected, the doxorubicin had reduced the heart’s function and size and increased fibrosis.

Sadly, the exercising mice had not been protected from this damage. However, the researchers discovered a surprise. “The tumor data — I find them actually amazing,” Libonati told Penn News. The mice that exercised while receiving chemotherapy had significantly smaller tumors than mice that only received the drug. “People don’t take a drug and then sit down all day,” said Libonati. “Something as simple as moving affects how drugs are metabolized.”

Libonati plans further studies to investigate precisely how exercise enhances the effect of doxorubicin, though they suspect it is a simple matter of exercise increasing blood flow to the tumor, bringing with it more of the drug. In any event, the accident of this scientific team's discovery is another one for the books.

Source: Sturgeon K, Schadler K, Muthukumaran G, et al. Concomitant low-dose doxorubicin treatment and exercise. American Journal of Physiology. 2014.