Green Tea Extract Possible Cancer Prevention Agent for Oral Cancer

According to a study conducted by researchers from the M. D. Anderson Cancer Center and published online in the Cancer Prevention Research journal, green tea extract shows promise as a cancer prevention agent for oral cancer in patients with a pre-malignant condition known as oral leukoplakia.

According to the American Cancer Society, more than 35,720 are expected to be diagnosed with oral and/or pharynx cancer and the five year survival rate is less than 50 percent.

In this first of a kind study to examine green tea as a cancer prevention agent in this high-risk patient population it was found that more than half of the oral leukoplakia patients who took the extract had a clinical response. Green tea is rich in polyphenols that have been known to inhibit carcinogenesis in preclinical models and has been extensively investigated in laboratory, epidemiological and clinical settings for several cancer types,

"While still very early and not definitive proof that green tea is an effective cancer preventive agent, these results certainly encourages more study for patients at highest risk for oral cancer," said Vassiliki Papadimitrakopoulou, 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."

In the Phase II dose-finding study, 41 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 - 500 per meter squared of body mass (mg/m2); 750 mg/m2 or 1,000 mg/m2 - 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.

"Collecting oral tissue biopsies was essential in that it allowed us to learn that not only did the green tea extract appear to have benefit for some patients, but we pointed to anti-angiogenic effects as a potential mechanism of action," said Anne Tsao, the study's first author. "While preliminary because our patient population was so small, this gives us direction for further study."

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. The extract was well tolerated and side effects, including insomnia and nervousness, were mostly seen in the high-dose group but produced no significant toxicity.

"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. "We need to further understand if green tea offers longer-term prevention effects for patients."

The researchers stressed that the green tea extract studied in this trial was never sold over-the-counter and/or the Internet, both of which are not highly regulated. Rather, the compound was exclusively developed as a pharmaceutical.

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References:
1. Vassiliki Papadimitrakopoulou, et al. Phase II Randomized, Placebo-Controlled Trial of Green Tea Extract in Patients with High-Risk Oral Premalignant Lesions. Cancer Prevention Research 2, 931, November 1, 2009. doi: 10.1158/1940-6207.CAPR-09-0121.