title: Does hormone therapy counter the beneficial effects of physical activity on breast cancer risk in postmenopausal women?
abstract: Studies consistently demonstrate that physical activity is inversely associated with postmenopausal breast cancer. Whether this association is stronger among non-hormone users or former users of menopausal hormone therapy (HT) is of interest given the marked decline in HT use since 2002. The Women's Contraceptive and Reproductive Experiences Study, a population-based case-control study of invasive breast cancer, recruited white women and black women ages 35-64 years and collected histories of lifetime recreational physical activity and HT use including estrogen-alone therapy (ET) and estrogen plus progestin therapy (EPT). Among postmenopausal women (1,908 cases, 2,013 control participants), breast cancer risk declined with increasing levels of lifetime physical activity among never HT users; among short-term HT users (fewer than 5 years); and among current ET users; P (trend) values ranged from 0.004 to 0.016. In contrast, physical activity had no significant association with risk among long-term and past HT users and among current EPT users. No statistical evidence of heterogeneity was demonstrated for duration or currency of HT use. Breast cancer risk decreases with increasing lifetime physical activity levels among postmenopausal women who have not used HT, have used HT for less than 5 years, or are current ET users, yet this study was unable to demonstrate statistically that HT use modifies the relationship between physical activity and breast cancer. With profound changes in HT use occurring since 2002, it will be important in future studies to learn whether or not any association between physical activity and breast cancer among former HT users is a function of time since last HT use.
authors.affiliation: Division of Cancer Etiology, Department of Population Sciences, City of Hope National Medical Center, 1500 East Duarte Road, Duarte, CA 91010, USA. cdielic@coh.org
authors.forename: Christina M
authors.initials: CM
authors.lastname: Dieli-Conwright
authors.forename: Jane
authors.initials: J
authors.lastname: Sullivan-Halley
authors.forename: Alpa
authors.initials: A
authors.lastname: Patel
authors.forename: Michael
authors.initials: M
authors.lastname: Press
authors.forename: Kathleen
authors.initials: K
authors.lastname: Malone
authors.forename: Giske
authors.initials: G
authors.lastname: Ursin
authors.forename: Ronald
authors.initials: R
authors.lastname: Burkman
authors.forename: Brian
authors.initials: B
authors.lastname: Strom
authors.forename: Michael
authors.initials: M
authors.lastname: Simon
authors.forename: Linda
authors.initials: L
authors.lastname: Weiss
authors.forename: Polly
authors.initials: P
authors.lastname: Marchbanks
authors.forename: Suzanne
authors.initials: S
authors.lastname: Folger
authors.forename: Robert
authors.initials: R
authors.lastname: Spirtas
authors.forename: Dennis
authors.initials: D
authors.lastname: Deapen
authors.forename: Leslie
authors.initials: L
authors.lastname: Bernstein
mesh_terms: D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000209:etiology* / Q000473:pathology; D016022:Case-Control Studies; D004967:Estrogens / Q000008:administration & dosage; D005260:Female; D020249:Hormone Replacement Therapy / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity; D017698:Postmenopause; D011372:Progestins / Q000008:administration & dosage; D044465:White People / Q000706:statistics & numerical data
chemical_list: D004967:Estrogens; D011372:Progestins