title: Postmenopausal Hormone Therapy and Breast Cancer Prognostic Characteristics: A Linkage between Nationwide Registries.
abstract: The effects of use of different types of hormone therapy on breast cancer risk according to prognostic factors are largely unknown.
  
  
  
  We linked data from the Norwegian Prescription Database and the Cancer Registry of Norway during 2004 to 2009 on all women ages 45 to 79 years (N = 686,614). We estimated rate ratios and 95% confidence intervals for breast cancer in relation to hormone therapy using Poisson regression.
  
  
  
  During an average 4.8 years of follow-up, 7,910 invasive breast cancers were diagnosed. Compared with nonusers of hormone therapy, users of estradiol and tibolone were more likely to be diagnosed with grade I, lymph node-negative, and estrogen receptor-positive (ER+)/progesterone receptor-positive (PR+) tumors. However, compared with nonusers, users of the most common estrogen and progestin combinations [estradiol-norethisterone acetate (NETA) preparations (Kliogest, Activelle or Trisekvens)] were at a 4- to 5-fold elevated risk of grade I tumors, 3-fold elevated risk of lymph node-negative tumors, and 3- to 4-fold elevated risk of ER+/PR+tumors. Importantly, estradiol-NETA users were also at a 2- to 3-fold increased risk of medium differentiated (grade II) tumors and tumors with lymph node involvement.
  
  
  
  Use of oral estradiol, tibolone, and estradiol-NETA predominantly increases the risk of breast cancer with favorable prognosis characteristics. However, use of estradiol-NETA preparations also increases the risk of breast cancers with less favorable characteristics.
  
  
  
  The hormone therapy preparations most commonly used in the Nordic countries are associated with both breast cancers with good and less favorable prognosis characteristics. Cancer Epidemiol Biomarkers Prev; 25(11); 1464-73. ©2016 AACR.
authors.affiliation: Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo, Norway.|Women and Children's Division, National Advisory Unit for Women's Health, Oslo University Hospital, Oslo, Norway.
authors.forename: Marta
authors.initials: M
authors.lastname: Román
authors.affiliation: Department of Chronic Diseases, Norwegian Institute of Public Health, Oslo, Norway.|Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, The Arctic University of Norway, Tromsø, Norway.
authors.forename: Sidsel
authors.initials: S
authors.lastname: Graff-Iversen
authors.affiliation: Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo, Norway.|Department of Community Medicine, Faculty of Health Sciences, University of Tromsø, The Arctic University of Norway, Tromsø, Norway.|Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.|Department of Genetic Epidemiology, Folkhälsan Research Center, Helsinki, Finland.
authors.forename: Elisabete
authors.initials: E
authors.lastname: Weiderpass
authors.affiliation: Women and Children's Division, National Advisory Unit for Women's Health, Oslo University Hospital, Oslo, Norway.
authors.forename: Siri
authors.initials: S
authors.lastname: Vangen
authors.affiliation: Department of Pharmacoepidemiology, Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: Solveig
authors.initials: S
authors.lastname: Sakshaug
authors.affiliation: Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo, Norway.|Oslo and Akershus University College of Applied Sciences, Faculty of Health Science, Oslo, Norway.
authors.forename: Solveig
authors.initials: S
authors.lastname: Hofvind
authors.affiliation: Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo, Norway. Giske.Ursin@kreftregisteret.no.|Department of Preventive Medicine, University of Southern California, California.|Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
authors.forename: Giske
authors.initials: G
authors.lastname: Ursin
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000453:epidemiology; D004338:Drug Combinations; D004958:Estradiol / Q000009:adverse effects; D004967:Estrogens / Q000009:adverse effects; D005260:Female; D020249:Hormone Replacement Therapy / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D009640:Norethindrone / Q000009:adverse effects; D009652:Norpregnenes / Q000009:adverse effects; D009664:Norway; D017698:Postmenopause; D011379:Prognosis; D012042:Registries; D012306:Risk
chemical_list: D004338:Drug Combinations; D004967:Estrogens; D009652:Norpregnenes; C418365:estradiol, norethindrone drug combination; D004958:Estradiol; C027385:tibolone; D009640:Norethindrone