Evidence continues to brew about the protective effects of green tea against cancer, but scientists are still not sure the tea leaves reveal the answer.
Vassiliki Papadimitrakopoulo, M.D., professor of medicine in the Department of Thoracic/Head and Neck Medical Oncology at the University of Texas M. D. Anderson Cancer Center, and colleagues tested 41 patients who took green tea extract orally for three months at three dose levels.
Nearly 60 percent of patients with oral pre-malignant lesions, who were at the highest dose levels, displayed clinical response, compared with less than 20 percent among those taking placebo. Researchers also observed a trend toward improved histology, and a trend toward improvement in a handful of biomarkers that may be important in predicting cancer development.
Patients were followed for 27.5 months, and at the end of the study period, 15 developed oral cancer. Although there was no difference in oral cancer development overall between those who took green tea extract and those who did not, patients who presented with mild to moderate dysplasia had a longer time to develop oral cancer if they took green tea extract.
Although encouraged by the results, Dr. Papadimitrakopoulo cautioned against any recommendations that green tea could definitely prevent cancer.
“This is a phase II study with a very limited number of patients who took what would be the equivalent of drinking eight to 10 cups of green tea every single day,” Dr. Papadimitrakopoulo was quoted as saying. “We cannot with certainty claim prevention benefits from a trial this size.”
Dong Shin, M.D., professor of hematology and medical oncology and Blomeyer Endowed Chair in Cancer Research at Emory School of Medicine, agreed, but indicated he thought this trial was certainly a step in the right direction.
“A clinical trial with a natural compound is no easy task, and these researchers have accomplished that,” Dr. Shin was quoted as saying. “The lack of toxicity is also important because often when you give supplements at higher doses than what would occur naturally, you induce nausea and vomiting. That did not happen in this trial.”
“The goal of this kind of research is to determine whether or not these supplements have long-term prevention effects,” Dr. Papadimitrakopoulou said. “More research including studies in which individuals at high risk are exposed to these supplements for longer time period is still needed to answer that sort of question.”
Source: Cancer Prevention Research, November, 2009