Potential of green tea extract to suppress colorectal polyp development in patients with familial adenomatous polyposis: a double-blind, randomized controlled trial Japan Familial Adenomatous Polyposis Prevention Study (J-FAPP Study I).

[BACKGROUND] Familial adenomatous polyposis (FAP) is an autosomal dominantly inherited disease that results in the development of more than 100 polyps, premalignant lesions, in the colorectum. Therefore, patients with FAP are a high-risk group for colorectal cancer (CRC). The only standard method of preventing CRC is total colectomy. Thus, alternative methods to prevent the development of CRC are desired by patients. Epidemiological and animal studies suggested that green tea and its extracts, such as (−)-epigallocatechin gallate, may have the potential to prevent cancer development.

[RESULTS] In the present study, we evaluated the suppressive effects of green tea extract (GTE) on suppress colorectal polyps in FAP and conducted a double-blind clinical trial. Eighty patients were randomly assigned to the GTE group (1.5 g/day for 2 years) and an equal number were assigned to the placebo group. The primary endpoint of colon polyp enlargement tended to be reduced in the GTE group compared with the placebo group, with a risk ratio of 0.43 (95% confidence interval 0.12–1.49;  = 0.16).

[CONCLUSIONS] Given that the risk ratio was less than 0.5 and few adverse events were observed, we believe that further research using GTE after calculating the necessary sample size is calculated on the based of this study, should be considered in a future large-scale clinical trial.