An extract from green tea may be able to fight oral cancer, according to a study from the M.D. Anderson Cancer Center.

A news release from the institute said that tests were performed on people who have oral leukoplakia, a pre-cancerous condition.

"While still very early, and not definitive proof that green tea is an effective preventive agent, these results certainly encourage more study for patients at highest risk for oral cancer," said Dr. Vassiliki Papadimitrakopoulou, the study's senior author. He also cited the extract's lack of toxicity.

In the study, 41 patients were given either the extract or a placebo for three months at various doses. Samples of the lesions were taken before and after the study.

More than half of those who took the extract at higher doses had a clinical response, the researchers said, compared with about one-third of those at lower doses and less than one in five of those who took the placebo.

"While these are encouraging findings, much more research must be done before we can conclude that green tea may prevent oral or any other type of cancer. It's also important to remind people that this trial enrolled very few participants who, at the highest dose levels, took the equivalent of eight cups of green tea three times a day," said Papadimitrakopoulo.

The study was funded by Ito En, the company that produced the green tea extract. It was published online in the journal Cancer Prevention Research.