title: Postmenopausal estrogen and progestin use in relation to breast cancer risk.
abstract: Epidemiological evidence now consistently supports a modest increase in breast cancer risk among women using postmenopausal hormones, usually estrogens. Less is known regarding how the addition of progestin affects breast cancer risk. The objective of this study was to investigate the type and duration of postmenopausal therapy and breast cancer risk. We performed a multicenter population-based case-control study set in Massachusetts, New Hampshire, and Wisconsin. The subjects were 5298 postmenopausal women (age range, 50-79 years) with a new diagnosis of invasive breast cancer from statewide tumor registries. For comparison, 5571 controls were randomly selected from population lists. Participants completed a structured telephone interview covering hormone use and breast cancer risk factors. Multivariable regression models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs). The RR for breast cancer increased with longer durations of hormone use, about 2%/year for estrogen alone (RR, 1.02; 95% CI, 1.01-1.03) and 4%/year for estrogen-progestin use (RR, 1.04; 95% CI, 1.01-1.08). Estrogen-progestin use that was both recent and long term (>5 years in duration) was more strongly associated with breast cancer risk (RR, 1.57; 95% CI, 1.15-2.14) than similar use of estrogen alone (RR, 1.39; 95% CI, 1.17-1.65). In estrogen-progestin users, risks were similar for sequential and continuous use regimens but perhaps stronger for lobular than ductal breast cancer. Use of progestin alone was associated with a doubling of risk (RR, 2.09; 95% CI, 1.07-4.07 for ever use versus nonuse). Estrogen-progestin use, both sequential and continuous, appears to be more strongly associated with risk of breast cancer than use of estrogen alone.
authors.affiliation: University of Wisconsin Comprehensive Cancer Center, Madison, Wisconsin 53706, USA.
authors.forename: Polly A
authors.initials: PA
authors.lastname: Newcomb
authors.forename: Linda
authors.initials: L
authors.lastname: Titus-Ernstoff
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Egan
authors.forename: Amy
authors.initials: A
authors.lastname: Trentham-Dietz
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
authors.forename: Barry E
authors.initials: BE
authors.lastname: Storer
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.forename: Meir J
authors.initials: MJ
authors.lastname: Stampfer
mesh_terms: D017677:Age Distribution; D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000453:epidemiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D016001:Confidence Intervals; D004338:Drug Combinations; D015914:Estrogen Replacement Therapy / Q000009:adverse effects / Q000379:methods; D005260:Female; D020249:Hormone Replacement Therapy / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D008404:Massachusetts / Q000453:epidemiology; D008875:Middle Aged; D016017:Odds Ratio; D017698:Postmenopause; D011336:Probability; D011372:Progestins / Q000008:administration & dosage / Q000009:adverse effects*; D012016:Reference Values; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D014922:Wisconsin / Q000453:epidemiology
chemical_list: D004338:Drug Combinations; D011372:Progestins