Thursday, November 5, 2009

Green Tea Extract as Chemoprevention Agent for Oral Cancer

Researchers at The University of Texas M. D. Anderson Cancer Center have been working with green tea extracts, and recently published the news that this extract has shown promise as a cancer prevention agent for oral cancer in patients with a pre-malignant condition known as oral leukoplakia.

Their study has been published online in Cancer Prevention Research, and is the first to examine green tea as a chemopreventative agent in this high-risk patient population. In studying the data after the study, researchers found that more than half of the oral leukoplakia patients who took the extract had a clinical response. This is significant because according to the American Cancer Society, more than 35,720 are expected to be diagnosed annually with oral and/or pharynx cancer and the five-year survival rate is less than 50 percent.

Green tea is rich in polyphenols, which have been known to inhibit carcinogenesis in preclinical models, and it has long been investigated in laboratory, epidemiological and clinical settings for several cancer types. We've written up many of these reports in this blog. Still, clinical results have been mixed.

"While still very early, and haven't yet had definitive proof that green tea is an effective preventive agent. These results certainly encourage more study for patients at the highest risk for oral cancer," said Vassiliki Papadimitrakopoulou, M.D., professor at M. D. Anderson and the study's senior author. "The extract's lack of toxicity is attractive - in prevention trials, it's very important to remember that these are otherwise healthy individuals and we need to ensure that agents studied produce no harm."

This was a Phase II dose-finding study, and 41 M. D. Anderson oral leukoplakia patients were randomized between August 2002 and March 2008 to receive either green tea extract or placebo. Participants took the extract, an oral agent, for three months at one of three doses, for three times daily. To best assess biomarkers, participants also underwent a baseline and 12-week biopsy, an important component in the design of the study, the researchers say.

Of those taking green tea at the two highest doses, 58.8 percent had a clinical response, compared with 36.4 percent in the lowest extract dose and 18.2 percent in the placebo arm. At an extended follow-up with a mean of 27.5 months, 15 participants had developed oral cancer, with a median time to disease development of 46.4 months.
Although not statistically significant, the green tea extract also improved histology and trended towards an improvement in a number of biomarkers that may play a vital role in predicting cancer development.

Another important finding, say the researchers, was that that the extract was well tolerated. Side effects, including insomnia and nervousness, were mostly seen in the high-dose group but produced no significant toxicity.The researchers said that the green tea extract studied in this trial was exclusively developed as a pharmaceutical.


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