Although drinking alcohol appears to increase the risk of developing breast cancer, drinking may be beneficial for those who already have the disease, a new study of mice suggests.

Of the mice in the study that had breast cancer, those that were given moderate to high levels of alcohol had fewer instances of cancer spreading to other parts of the body than alcohol-free mice did.

The study is one of the first to look at the effect of drinking on cancer metastasis, said study researcher Gary Meadows, a professor of pharmacy at Washington State University.

However, Meadows said it's important to conduct further studies so that doctors can best advise breast cancer patients on the risks and benefits of consuming alcohol after diagnosis. Whether humans would experience the same effect is unknown, and in any case, it could be impractical as a treatment: The mice that fared best in the study drank so much alcohol that if they were people, they probably would be considered alcoholics, Meadows said.

The findings were presented Nov. 3 at the American Institute for Cancer's annual meeting in Washington, D.C.

Reducing cancer spread

For the study, tumors were injected into mice's mammary glands (where breast cancer usually originates), and the mice were then divided into four groups. Three groups drank water mixed with differing levels of alcohol (low, moderate or high), and the fourth group drank only water.

After four weeks, the researchers checked the mice to see if the cancer had spread to their lungs.

Mice who drank water spiked with a high dose of alcohol were 60 percent less likely to develop metastases in their lungs than those that drank plain water.

Some protection against metastases was seen in mice in the moderate-dose group, but none was seen in the low-dose group.

The researchers aren't sure how alcohol, which is carcinogenic, may act to suppress breast cancer's spread. The study showed alcohol did not affect the growth of tumors in the breast. So it may have affected the spread of the tumor in a different way, such as allowing the immune system to better attack the cancer at other sites in the body.

Alcohol therapy?

Although we don't know what effect alcohol has on metastases in people, the study "provides some clues as to what could potentially occur," said Somdat Mahabir, a nutritional epidemiologist at the National Institutes of Health, who was not involved with the study.

Previous studies showed alcohol can reduce metastases in animals with certain types of skin cancer.

Although alcohol has toxic effects, it could still theoretically be a treatment.

"I'm not opposed to anything that may have a therapeutic effect," Mahabir said. "But we need to weigh the risks versus the benefits."

Studies that ask questions about alcohol consumption before and after cancer diagnosis, and that follow patients over time, could provide a better idea of how alcohol affects cancer metastases in people, Mahabir said.

Pass it on: High doses of alcohol suppress the spread of breast cancer tumors in mice.