ANAHEIM, CALIF. — An extract of the catechins found in green tea appears to be effective in preventing the progression of high-grade prostatic intraepithelial neoplasia to invasive prostate cancer, Saverio Bettuzzi, Ph.D., reported at the annual meeting of the American Association for Cancer Research.
In the placebo-controlled, double-blind study, 30 men with prostatic intraepithelial neoplasia (PIN) took 200 mg of green tea catechins (GTCs) three times daily for 6 months. Another 30 men with PIN took a placebo.
Catechins are antioxidants, and they belong to a class of polyphenols called flavanols. Epigallocatechin-3-gallate (EGCG) is the major catechin in green tea, and in tissue culture EGCG has been shown to induce apoptosis in cancer cells, but not normal cells.
All the participants underwent biopsies at study entry and 6 and 12 months later.
At 12 months, nine (30%) of the men who took placebo had progressed to prostate cancer. Only one (3.3%) of the men who took GTC had progression of PIN to invasive cancer, for an apparent efficacy rate of 90%. The difference between the groups was statistically significant.
The participants were aged 5–75 years. Men who drank green tea, who were vegetarians, or who were taking antioxidants or antiandrogenic therapy were excluded from the study.
Dr. Bettuzzi, of the University of Parma (Italy), said that previous studies have shown that about 30% of men with PIN will typically progress to invasive prostate cancer within a year, the same rate as in the placebo arm of his study.
No serious adverse events occurred among the men taking GTCs.
The investigators measured levels of prostate-specific antigen (PSA) every 3 months during the course of the study. They noted no significant differences in PSA levels between the two groups.
GTCs were extracted in the laboratory, although Dr. Bettuzzi said that green tea extracts are also available commercially. The 600-mg daily dose of GTCs corresponds to about 12–15 cups of green tea daily. He said that 10–20 cups of green tea is the normal daily intake in China.
Dr. Bettuzzi said he had no financial conflicts related to the study, which was supported in part by Genprofiler GmbH, a company in Bolzano, Italy, that manufactures diagnostics for molecular biology.