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Randomized Controlled Trial
. 2015 Oct;26(10):1405-19.
doi: 10.1007/s10552-015-0632-2. Epub 2015 Jul 24.

The Minnesota Green Tea Trial (MGTT), a randomized controlled trial of the efficacy of green tea extract on biomarkers of breast cancer risk: study rationale, design, methods, and participant characteristics

Hamed Samavat  1 , Allison M Dostal  1 , Renwei Wang  2 , Sarah Bedell  1 , Tim H Emory  3 , Giske Ursin  4   5   6 , Carolyn J Torkelson  7 , Myron D Gross  8 , Chap T Le  9   10 , Mimi C Yu  6 , Chung S Yang  11 , Douglas Yee  10   12   13 , Anna H Wu  6 , Jian-Min Yuan  2   14 , Mindy S Kurzer  15
Affiliations
Randomized Controlled Trial

The Minnesota Green Tea Trial (MGTT), a randomized controlled trial of the efficacy of green tea extract on biomarkers of breast cancer risk: study rationale, design, methods, and participant characteristics

Hamed Samavat et al. Cancer Causes Control. 2015 Oct.

Abstract

Purpose: The Minnesota Green Tea Trial (MGTT) was a randomized, placebo-controlled, double-blinded trial investigating the effect of daily green tea extract consumption for 12 months on biomarkers of breast cancer risk.

Methods: Participants were healthy postmenopausal women at high risk of breast cancer due to dense breast tissue with differing catechol-O-methyltransferase (COMT) genotypes. The intervention was a green tea catechin extract containing 843.0 ± 44.0 mg/day epigallocatechin gallate or placebo capsules for 1 year. Annual digital screening mammograms were obtained at baseline and month 12, and fasting blood and 24-h urine samples were provided at baseline and at months 6 and 12. Primary endpoints included changes in percent mammographic density, circulating endogenous sex hormones, and insulin-like growth factor axis proteins; secondary endpoints were changes in urinary estrogens and estrogen metabolites and circulating F2-isoprostanes, a biomarker of oxidative stress.

Results: The MGTT screened more than 100,000 mammograms and randomized 1,075 participants based on treatment (green tea extract vs. placebo), stratified by COMT genotype activity (high COMT vs. low/intermediate COMT genotype activity). A total of 937 women successfully completed the study and 138 dropped out (overall dropout rate = 12.8 %).

Conclusions: In this paper we report the rationale, design, recruitment, participant characteristics, and methods for biomarker and statistical analyses.

Keywords: Breast cancer; Green tea; Mammographic density; Postmenopausal women; Sex hormones.

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Conflict of interest statement

Disclosure of Potential Conflicts of Interest: No potential conflicts of interest are disclosed.

Figures

Fig. 1
Fig. 1
Flow Diagram of Participant Screening, Enrollment, Randomization, and Follow-up of the Minnesota Green Tea Trial, Minnesota, 2009–2014 Abbreviations: BMI, body mass index; COMT, catechol-O-methyltransferase; GTE, green tea extract; HRT, hormone replacement therapy; ITT, intention-to-treat
See this image and copyright information in PMC

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