Bone mineral density and endogenous hormones and risk of breast cancer in postmenopausal women (United States).
OBJECTIVE
This case-cohort study was designed to examine whether total hip bone mineral density (BMD) is independently associated with breast cancer over and above its association with other determinants, including levels of total and bioavailable estradiol and testosterone and sex-hormone binding globulin.


METHODS
Our study population was selected from a cohort of 8,203 postmenopausal women who were screened for the Fracture Intervention Trial in 1992, at which time BMD was assessed, and blood samples were obtained. A total of 109 women developed breast cancer during four years of follow-up; 173 other randomly selected women from the larger cohort were also selected. Cox proportional hazards with robust variance adjustment was used for these analyses.


RESULTS
Relative to women in the lower fourth of the BMD distribution, the risk associated with being in the upper fourth was 2.6 (95% confidence interval (CI) 1.1-5.8). After adjusting for serum hormone levels, the corresponding relative risk was 2.5 (95% CI 0.9-5.2). With body mass index and number of years since menopause added to the multivariate analysis, the relative risk decreased to 1.4 (95% CI 0.5-4.0).


CONCLUSIONS
BMD may not influence breast cancer risk independent of its relationship with endogenous hormones and measured covariates.
Buist
D S
DS
Center for Health Studies, Group Health Cooperative, Seattle, WA 98101, USA. buist.d@ghc.org
LaCroix
A Z
AZ
Barlow
W E
WE
White
E
E
Cauley
J A
JA
Bauer
D C
DC
Weiss
N S
NS
D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D001943:Breast Neoplasms / Q000097:blood / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D002140:California / Q000453:epidemiology; D016022:Case-Control Studies; D015331:Cohort Studies; D004958:Estradiol / Q000097:blood; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006615:Hip; D006801:Humans; D007484:Iowa / Q000453:epidemiology; D008875:Middle Aged; D009922:Oregon / Q000453:epidemiology; D015663:Osteoporosis, Postmenopausal / Q000097:blood / Q000150:complications* / Q000453:epidemiology / Q000503:physiopathology; D016016:Proportional Hazards Models; D012306:Risk; D012307:Risk Factors; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013739:Testosterone / Q000097:blood; D014861:Washington / Q000453:epidemiology
D012739:Gonadal Steroid Hormones; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone; D004958:Estradiol