title: 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.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA.
authors.forename: Hamed
authors.initials: H
authors.lastname: Samavat
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA.
authors.forename: Allison M
authors.initials: AM
authors.lastname: Dostal
authors.affiliation: Division of Cancer Control and Population Sciences, University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA.
authors.forename: Renwei
authors.initials: R
authors.lastname: Wang
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Bedell
authors.affiliation: Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Tim H
authors.initials: TH
authors.lastname: Emory
authors.affiliation: Cancer Registry of Norway, Oslo, Norway.|Department of Nutrition, University of Oslo, Oslo, Norway.|Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, CA, USA.
authors.forename: Giske
authors.initials: G
authors.lastname: Ursin
authors.affiliation: Department of Family Medicine and Community Health, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Carolyn J
authors.initials: CJ
authors.lastname: Torkelson
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis, MN, USA.
authors.forename: Myron D
authors.initials: MD
authors.lastname: Gross
authors.affiliation: Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN, USA.|Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Chap T
authors.initials: CT
authors.lastname: Le
authors.affiliation: Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, CA, USA.
authors.forename: Mimi C
authors.initials: MC
authors.lastname: Yu
authors.affiliation: Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, NJ, USA.
authors.forename: Chung S
authors.initials: CS
authors.lastname: Yang
authors.affiliation: Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA.|Department of Medicine, University of Minnesota, Minneapolis, MN, USA.|Department of Pharmacology, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Yee
authors.affiliation: Department of Preventive Medicine, University of Southern California Keck School of Medicine, Los Angeles, CA, USA.
authors.forename: Anna H
authors.initials: AH
authors.lastname: Wu
authors.affiliation: Division of Cancer Control and Population Sciences, University of Pittsburgh Cancer Institute, Pittsburgh, PA, USA.|Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Yuan
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA. mkurzer@umn.edu.
authors.forename: Mindy S
authors.initials: MS
authors.lastname: Kurzer
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage; D015415:Biomarkers / Q000378:metabolism*; D001940:Breast / Q000033:anatomy & histology*; D001943:Breast Neoplasms / Q000517:prevention & control*; D002392:Catechin / Q000008:administration & dosage / Q000031:analogs & derivatives; D002394:Catechol O-Methyltransferase / Q000235:genetics; D004311:Double-Blind Method; D004967:Estrogens / Q000652:urine; D028441:F2-Isoprostanes / Q000097:blood; D005260:Female; D005838:Genotype; D012739:Gonadal Steroid Hormones / Q000097:blood; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008327:Mammography; D008875:Middle Aged; D008910:Minnesota; D018384:Oxidative Stress; D012307:Risk Factors; D013662:Tea
chemical_list: D000975:Antioxidants; D015415:Biomarkers; D004967:Estrogens; D028441:F2-Isoprostanes; D012739:Gonadal Steroid Hormones; D013662:Tea; D007334:Insulin-Like Growth Factor I; D002392:Catechin; C045651:epigallocatechin gallate; D002394:Catechol O-Methyltransferase
keywords: Breast cancer; Green tea; Mammographic density; Postmenopausal women; Sex hormones