ROCHESTER, Minn. -- Although the benefits of green tea are widely touted, a study conducted by Mayo Clinic Cancer Center and North Central Cancer Treatment Group shows green tea is not an effective treatment for advanced prostate cancer.
“Previous laboratory studies suggested that green tea might be an effective anticancer treatment,” says Aminah Jatoi, M.D., a Mayo Clinic medical oncologist and lead researcher on the study. “However, in our study of 42 patients with advanced androgen-independent prostate cancer, only one patient showed a short-term drop in his prostate-specific antigen (PSA) levels.
“Our conclusion is that for the treatment of advanced prostate cancer, green tea does not provide therapeutic benefit,” Dr. Jatoi says.
The phase II study is the first to test the effects of green tea in patients with advanced prostate cancer. The results of the study will be published in the March 15 issue of the journal Cancer.
Prostate cancer is the most common cancer in men age 65 and older, and the second leading cause of cancer death among men in the United States. This year, about 200,000 men will be diagnosed with prostate cancer and about 28,000 men will die from the disease. The PSA is a blood test commonly used to detect and monitor prostate cancer. Conventional treatment is based on disease stage and PSA levels, and treatment response is monitored in part by the rise and fall of PSA levels.
Androgens are male hormones that stimulate the growth of prostate cancer. Even though the men in the study had had their male hormones suppressed in an effort to stop tumor growth, their PSA levels indicated the cancer was continuing to grow and spread.
“Since men with androgen-independent prostate cancer have few treatment options, we chose this group of patients for our green tea trial to learn whether green tea might help them,” says Dr. Jatoi. “It was an effort to try to find other ways to treat these patients even if those ways might be considered by some to be unconventional.”
Laboratory studies have indicated that prostate cancer cells die when exposed to compounds called polyphenols found in green tea. In mice with prostate cancer, green tea has been shown to decrease tumor size and cancer spread. Epidemiological studies suggest that tea decreases the risk of prostate cancer. Such studies suggested that green tea might be an effective treatment for patients with prostate cancer.
The study required each patient to take 6 grams a day of a highly concentrated, presweetened tea. The patients could drink the green tea as they wished -- hot, iced, in juice or with additional sweetener.
“We set the dosage at the highest, yet relatively tolerable level, so patients could potentially receive maximal therapeutic benefit,” says Dr. Jatoi.
At the start of the study, all patients reported drinking the specified amounts of green tea daily. After about one month, researchers found patients were dropping out of the study because their prostate cancer was not regressing and because of side effects attributed to the high-dose green tea.
“No patient experienced a sustained decline in PSA levels,” says Dr. Jatoi. “One patient had a one-month decline but rebounded by the second month with increasing PSA levels.”
In addition, 69 percent of patients reported mild side effects of diarrhea, nausea, vomiting and abdominal pain. Seventeen percent of the patients had moderate to severe side effects, including insomnia, diarrhea and confusion.
“Green tea failed to show an anticancer effect in the group of patients we studied,” says Dr. Jatoi. “We concluded that other avenues should be explored in the treatment of patients with androgen-independent prostate cancer.”