Hormone replacement therapy and risk of breast cancer: the role of progestins.
Epidemiological studies have shown an increased risk of breast cancer associated with the use of hormone replacement therapy (HRT). This notion is mostly based on studies from the USA. During the last decades unopposed estrogen treatment has been used to a lesser extent, whereas the combined estrogen-progestin treatment regime is now prescribed worldwide. In the USA the predominant compounds are conjugated estrogens and medroxyprogesterone-acetate, whereas oestradiol combined with testosterone-like progestins is commonly used in Europe. These differences are largely the result of traditions. Recent studies originating from both the USA and Europe suggest that the combined treatment regimens with estrogen and progestin increase the risk of breast cancer beyond the risk following the use of unopposed estrogen. At present it is not known if progestins with different androgenicity influence the risk of breast cancer to a varying degree. This review focuses on studies published after the latest meta-analysis in 1997, with special attention given to the type of progestin used and the treatment mode, i.e., cyclical or continuous regimen.
Stahlberg
Claudia
C
Department of Obstetrics and Gynecology, H:S Hvidovre Hospital, University of Copenhagen, Hvidovre, Denmark. c.stahlberg@dadlnet.dk
Pederson
Anette Tønnes
AT
Lynge
Elsebeth
E
Ottesen
Bent
B
D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D004334:Drug Administration Schedule; D016021:Epidemiologic Studies; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000008:administration & dosage; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage; D015201:Meta-Analysis as Topic; D008875:Middle Aged; D009640:Norethindrone / Q000008:administration & dosage / Q000031:analogs & derivatives*; D000077563:Norethindrone Acetate; D011372:Progestins / Q000008:administration & dosage*; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
D011372:Progestins; D016912:Levonorgestrel; D000077563:Norethindrone Acetate; D017258:Medroxyprogesterone Acetate; D009640:Norethindrone