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Green Tea Extracts for the Prevention of Metachronous Colorectal Adenomas: A Pilot Study

¹ Department of Medicine, Gifu University Graduate School of Medicine; ² Gifu Prefectural General Medical Center; ³ Gihoku Kousei Hospital; ⁴ Gifu Municipal Hospital, Gifu, Japan; ⁵ Research Institute for Clinical Oncology, Saitama Cancer Center, Saitama, Japan; and ⁶ Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima, Japan

Requests for reprints: Hisataka Moriwaki, Department of Medicine, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu 501-1194, Japan. Phone: 81-58-230-6308; Fax: 81-58-230-6310; E-mail: hmori{at}gifu-u.ac.jp.

Background: Experimental studies indicate the chemopreventive properties of green tea extract (GTE) on colorectal cancer. Epidemiologically, green tea consumption of >10 cups daily reduced colorectal cancer risk in Japanese. Because colorectal adenomas are the precursors to most sporadic colorectal cancers, we conducted a randomized trial to determine the preventive effect of GTE supplements on metachronous colorectal adenomas by raising green tea consumption in the target population from an average of 6 cups (1.5 g GTE) daily to 10 cups equivalent (2.5 g GTE) by supplemental GTE tablets.

Methods: We recruited 136 patients, removed their colorectal adenomas by endoscopic polypectomy, and 1 year later confirmed the clean colon (i.e., no polyp) at the second colonoscopy. The patients were then randomized into two groups while maintaining their lifestyle on green tea drinking: 71 patients supplemented with 1.5 g GTE per day for 12 months and 65 control patients without supplementation. Follow-up colonoscopy was conducted 12 months later in 125 patients (65 in the control group and 60 in the GTE group).

Results: The incidence of metachronous adenomas at the end-point colonoscopy was 31% (20 of 65) in the control group and 15% (9 of 60) in the GTE group (relative risk, 0.49; 95% confidence interval, 0.24-0.99; P < 0.05). The size of relapsed adenomas was also smaller in the GTE group than in the control group (P < 0.001). No serious adverse events occurred in the GTE group.

Conclusion: GTE is an effective supplement for the chemoprevention of metachronous colorectal adenomas. (Cancer Epidemiol Biomarkers Prev 2008;17(11):3020–5)