Exercise May Make Tumors Less Aggressive, More Likely to Respond to Treatment

close up of man's and woman's legs as they walk through grass

Exercise may have yet another benefit – the right amount at the right time could make cancer treatments such as radiation and chemotherapy more effective.

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.

“Hypoxia 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.”

Behnke 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

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.

“We 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.

However, 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.”

Given 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 aggressive.”

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