EXERCISE BOOSTS TUMOR -FIGHTING ABILITY OF CHEMOTHERAPY
Study after study has
proven it true: exercise is good for you. But new research from University of
Pennsylvania scientists suggests that exercise may have an added benefit for
cancer patients undergoing chemotherapy
Their work, performed
in a mouse model of melanoma, found that combining exercise with chemotherapy
shrunk tumors more than chemotherapy alone.
Joseph Libonati, an
associate professor in the School of Nursing and director of the Laboratory of
Innovative and Translational Nursing Research, was the senior author on the
study, which appears in the American Journal of Physiology. His
collaborators included Penn Nursing's Geetha Muthukumaran, Dennis Ding and
Akinyemi Bajulaiye plus Kathleen Sturgeon, Keri Schadler, Nicholas J. Thomas,
Victor Ferrari and Sandra Ryeom of Penn's Perelman School of Medicine.
Exercise has long been
recommended to cancer patients for its physical and psychological benefits.
Libonati 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."
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 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 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 two weeks than mice that
only received doxorubicin.
Further studies will
investigate exactly how exercise enhances the effect of doxorubicin, but the
Penn team believes it could be in part 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.
Gaining a clearer
understanding of the many ways that exercise affects various systems of the
body could also pave the way for developing drugs that mimic the effects of
exercise.
"People don't
take a drug and then sit down all day," Libonati says. "Something as
simple as moving affects how drugs are metabolized. We're only just beginning
to understand the complexities."
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