Green tea extracts for the prevention of metachronous colorectal adenomas: a pilot study

Cancer Epidemiol Biomarkers Prev. 2008 Nov;17(11):3020-5. doi: 10.1158/1055-9965.EPI-08-0528.

Abstract

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 > or = 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoma / prevention & control*
  • Adult
  • Aged
  • Colonoscopy
  • Colorectal Neoplasms / prevention & control*
  • Female
  • Humans
  • Incidence
  • Japan
  • Male
  • Middle Aged
  • Neoplasms, Second Primary / prevention & control*
  • Pilot Projects
  • Plant Extracts*
  • Tea*
  • Treatment Outcome

Substances

  • Plant Extracts
  • Tea