(Xinhua)
Updated: 2008-04-14 13:51

WASHINGTON -- Prostate tumors grew more quickly in mice who exercised than in those who did not, leading to speculation that exercise may increase blood flow to tumors, according to a new study by a team of US researchers.

"Our study showed that exercise led to significantly greater tumor growth than a more sedentary lifestyle did, in this mouse model," said lead researcher Lee Jones from Duke University in the United States.

"We may, in the future, be able to use this finding to design better drug delivery models to more effectively treat prostate cancer patients, and those with other types of cancer as well."

The findings were presented Sunday at the annual meeting of the American Association for Cancer Research.

Researchers implanted prostate tumors subcutaneously in the flanks of 50 mice and then put half of the mice in cages with exercise wheels and half in cages with no wheels. All mice were fed the same diet. On average, the exercising mice ran more than half a mile each day.

"We found that among the mice that had the opportunity to voluntarily exercise, tumors grew approximately twice as fast as they did among the mice that did not have the opportunity to exercise," Jones said.

Researchers know that a challenge in delivering chemotherapy and radiation to tumors can be their poor blood flow, so these findings may hint at a way in which to improve blood flow to tumors, perhaps then allowing for better distribution of medicine, he said.

The researchers are currently conducting a validation study, in mice, in which tumors are injected directly into the prostate, thereby better simulating human prostate cancer, Jones said.

"Down the line, we will test this hypothesis in humans undergoing medical treatment for prostate cancer," he said.

The researchers want to caution men against interpreting these findings as an endorsement for not exercising for fear of getting or exacerbating cancer.

"These mice were not receiving treatment and we were allowing aggressive tumors to grow unchecked for the sake of the experiment," said study investigator Freedland, a urologist at Duke. "Patients would not find themselves in the same situation."