close up of man's and woman's legs as they walk through grass
may have yet another benefit – the right amount at the right time could
make cancer treatments such as radiation and chemotherapy more
The reason has to do with
blood flow delivery and oxygen, according to Bradley Behnke, Ph.D., a
physiology researcher at Kansas State University. “Tumors contain areas
of low oxygen (termed hypoxia), which make them resistant to
radiotherapy and more likely to metastasize,” says Behnke. Exercise
appears to combat this issue – increasing the amount of blood flow to
the tumor, resulting in better oxygenation of the tumor.
is a common phenomenon which occurs in almost every solid tumor –
brain, lung, breast, and prostate – and if the tumor is hypoxic, the
prognosis for the patient is poor, resulting in significantly shorter
survival and recurrence-free survival of patients versus those with a
non-hypoxic tumor,” says Behnke. “But exercise training seems to
alleviate this hypoxia almost completely.”
says that exercise changes the tumor environment and may influence the
effectiveness of treatment with radiation and, potentially, with
chemotherapy. “For example, there are exciting new studies that
demonstrate, in preclinical models, that chemotherapy plus exercise
results in a significantly prolonged growth delay of breast tumors
versus chemotherapy alone,” says Behnke.
Behnke’s prior studies in rats with prostate cancer, the results of which were published last year in the Journal of the National Cancer Institute,
found that low-to-moderate intensity exercise increased blood flow to
tumors by about 200% and decreased tumor hypoxia by about 50%. “We saw
that during exercise, as well as after long-term exercise training,
there was a greater reduction in hypoxia (up to 90% after training)
versus that which occurs with other conventional treatments for tumor
hypoxia such as high-oxygen breathing therapy.”

Finding the Right Exercise Amount, Intensity, and Timing 

Dr. Bradley Behnke



with the help of a $760,000 grant from the American Cancer Society,
Behnke is trying to figure out the specifics – how much and when a
cancer patient needs to exercise to decrease tumor hypoxia and increase
the effectiveness of treatment.
“We are
now exercise-training rats with prostate tumors and looking at how long
after the exercise the increase in oxygen to the tumors lasts, so that
we can determine the ideal timing for exercise therapy for cancer
“Our preliminary data shows
that the impact of exercise on the tumor environment lasts at least up
to two weeks after training.” Behnke’s next step is to test the impact
of the exercise training on the effectiveness of radiation treatment in
In his current study, Behnke is
focused on moderate-intensity exercise, such as brisk walking or slow
jogging. Behnke says it is important to figure out the exact right
exercise intensity level for cancer patients because too much exercise
(in terms of duration or intensity) may actually be a bad thing when it
comes to treating tumors.

have to figure out what the correct exercise protocols are, we can’t
just tell a patient to go exercise.” says Behnke. “Think about if you
tell someone one vitamin is good and then when they feel sick they take
3; well, what if you tell cancer patients exercise is good and then they
go and do heavy exercise that may compromise immune function and
potentially make the tumor worse?” This is why Behnke wants to find the
specific exercise model that is most beneficial for treatment outcomes.
Behnke notes that organizations including the American Cancer Society
already recommend exercise for cancer patients and survivors to help
them deal with the emotional and physical side effects of treatment.
“Based on this, I think the results of our research are going to be very
positive; I don’t think there is any data to suggest that a human
shouldn’t exercise before, during, and after cancer treatment.”

that radiation therapy is used for about 60% of cancer patients, Behnke
hopes his findings demonstrating the positive influence of exercise on
tumor treatment could translate into a helpful strategy for many
different types of cancers. “This is a way for us to change the tumor
microenvironment to be more beneficial and not as chaotic or