Influence of estrogen plus testosterone supplementation on breast cancer.
BACKGROUND
Concern that the use of exogenous testosterone may increase breast cancer risk coexists with rising use of this medication in the United States. We sought to examine the relationship between the use of estrogen plus testosterone (E + T) therapy (esterified estradiol plus methyltestosterone) and the occurrence of breast cancer.


METHODS
A total of 31,842 postmenopausal participants in the Women's Health Initiative Observational Study were followed for a mean of 4.6 years. At the 3-year visit, E + T users were compared with non-hormone therapy users for time to incident invasive breast cancer. Cox proportional hazards estimates were adjusted for known predictors of breast cancer including prior hormone use and screening mammography.


RESULTS
Thirty five women using E + T at visit 3 developed invasive breast cancer. Use of E + T had a nonsignificant impact on invasive breast cancer risk (adjusted hazard ratio, 1.42; 95% confidence interval, 0.95-2.11). The most commonly used E + T preparation, Estratest, was associated with a significant elevation in invasive breast cancer (adjusted hazard ratio, 1.78; 95% confidence interval, 1.05-3.01). However, rates of breast cancer were lower in longer-term E + T users than in shorter-term E + T users.


CONCLUSIONS
Although our results have less strength than an initial report linking E + T to breast cancer, we found a modest, albeit nonsignificant, elevation in breast cancer risk associated with E + T use.
Ness
Roberta B
RB
Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. roberta.b.ness@uth.tmc.edu
Albano
Jessica D
JD
McTiernan
Anne
A
Cauley
Jane A
JA
D000368:Aged; D000704:Analysis of Variance; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology* / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000453:epidemiology* / Q000209:etiology* / Q000473:pathology; D016022:Case-Control Studies; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004338:Drug Combinations; D004958:Estradiol / Q000009:adverse effects* / Q000627:therapeutic use; D005260:Female; D005500:Follow-Up Studies; D020249:Hormone Replacement Therapy / Q000009:adverse effects / Q000379:methods; D006801:Humans; D053208:Kaplan-Meier Estimate; D008327:Mammography; D008777:Methyltestosterone / Q000009:adverse effects* / Q000627:therapeutic use; D008875:Middle Aged; D017698:Postmenopause / Q000187:drug effects; D015995:Prevalence; D011336:Probability; D016016:Proportional Hazards Models; D012016:Reference Values; D012189:Retrospective Studies; D018570:Risk Assessment; D015996:Survival Rate
D004338:Drug Combinations; D004958:Estradiol; D008777:Methyltestosterone