title: Age-related variation in the relationship between menopausal hormone therapy and the risk of dying from breast cancer.
abstract: Multiple past studies have reported a reduced risk of breast cancer-related mortality (BCM) in relation to pre-diagnostic use of hormone therapy (HT); however, the extent to which this reduction is due to heightened screening or tumor biology is unknown. Using a population-based cohort of 1,911 post-menopausal women diagnosed with invasive breast cancer at ages 45-79 from 1993 to 1999, we investigated the extent to which the reduced risk in BCM observed in relation to HT might be explained by screening patterns or tumor features. Estrogen-progestin therapy (EPT) use was associated with a decreased risk of BCM (after adjustment for age, study, mammography, stage, and treatment), but only among older women (ever use: ≥ 65 years: HR = 0.45 [95% CI 0.26-0.80]; <65 years: HR = 1.03 [95% CI 0.60-1.79]). Estrogen-alone therapy (ET) use was not associated with risk of BCM (ever use: ≥ 65 years: HR = 0.76 [95% CI 0.51-1.12]; <65 years: HR = 1.20 [95% CI 0.71-2.02]). HT users had a much greater frequency of mammography (P value <0.001). EPT use was associated with tumor characteristics related to improved prognosis in older women after adjustment for screening, including an inverse association with poorly differentiated tumors (OR = 0.57 [95% CI 0.38-0.85]) and an association with lobular tumors (OR = 1.68 [95% CI 1.07-2.65]). Beyond the influence of EPT use on screening uptake, these data indicate that the improved survival associated with pre-diagnostic EPT use may be due in part to the development of more favorable tumor characteristics.
authors.affiliation: Department of Epidemiology, University of Washington School of Public Health, Seattle, WA, USA.
authors.forename: Kerryn W
authors.initials: KW
authors.lastname: Reding
authors.forename: David R
authors.initials: DR
authors.lastname: Doody
authors.forename: Anne
authors.initials: A
authors.lastname: McTiernan
authors.forename: Li
authors.initials: L
authors.lastname: Hsu
authors.forename: Scott
authors.initials: S
authors.lastname: Davis
authors.forename: Janet R
authors.initials: JR
authors.lastname: Daling
authors.forename: Peggy L
authors.initials: PL
authors.lastname: Porter
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Malone
mesh_terms: D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000401:mortality*; D002454:Cell Differentiation; D004967:Estrogens / Q000378:metabolism; D005260:Female; D020249:Hormone Replacement Therapy / Q000009:adverse effects*; D006728:Hormones / Q000627:therapeutic use*; D006801:Humans; D008327:Mammography / Q000379:methods; D008593:Menopause; D008875:Middle Aged; D016017:Odds Ratio; D011372:Progestins / Q000378:metabolism; D012306:Risk
chemical_list: D004967:Estrogens; D006728:Hormones; D011372:Progestins