Green tea fails to help prostate cancer patients
cancer, say researchers reporting on a small in-vivo study,
although the plant has previously been shown to decrease tumour
size and cancer spread in mice.
Green tea is not an effective treatment for advanced prostate cancer, say researchers, although the plant has been associated with many other health benefits.
Researchers at the Mayo Clinic Cancer Center and North Central Cancer Treatment Group in the US noted that as green tea had a high antioxidant level, it may be an effective anticancer treatment. But in a 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 (a marker for prostate cancer).
Dr Aminah Jatoi, a Mayo Clinic medical oncologist and lead researcher on the study, said: "Our conclusion is that for the treatment of advanced prostate cancer, green tea does not provide therapeutic benefit."
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 15 March 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. 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.
Even though the men in the study had had their male hormones (androgens) suppressed in an effort to stop tumour growth, their PSA levels indicated the cancer was continuing to grow and spread, reported the researchers.
"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," said 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 tumour size and cancer spread. Epidemiological studies have also suggested that tea decreases the risk of prostate cancer.
The study required each patient to take 6 grams a day of a highly concentrated, pre-sweetened 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," said 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.
None of the patients experienced a sustained decline in PSA levels. One patient had a one-month decline but rebounded by the second month with increasing PSA levels, said Dr Jatoi.
In addition, 69 per cent of patients reported mild side effects of diarrhoea, nausea, vomiting and abdominal pain. Seventeen per cent of the patients had moderate to severe side effects, including insomnia, diarrhoea and confusion.
"Green tea failed to show an anticancer effect in the group of patients we studied," said Dr Jatoi. "We concluded that other avenues should be explored in the treatment of patients with androgen-independent prostate cancer."
