Relationship between mammographic density and breast cancer death in the Breast Cancer Surveillance Consortium.
BACKGROUND
Women with elevated mammographic density have an increased risk of developing breast cancer. However, among women diagnosed with breast cancer, it is unclear whether higher density portends reduced survival, independent of other factors.


METHODS
We evaluated relationships between mammographic density and risk of death from breast cancer and all causes within the US Breast Cancer Surveillance Consortium. We studied 9232 women diagnosed with primary invasive breast carcinoma during 1996-2005, with a mean follow-up of 6.6 years. Mammographic density was assessed using the Breast Imaging Reporting and Data System (BI-RADS) density classification. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated by Cox proportional hazards regression; women with scattered fibroglandular densities (BI-RADS 2) were the referent group. All statistical tests were two-sided.


RESULTS
A total of 1795 women died, of whom 889 died of breast cancer. In multivariable analyses (adjusted for site, age at and year of diagnosis, American Joint Committee on Cancer stage, body mass index, mode of detection, treatment, and income), high density (BI-RADS 4) was not related to risk of death from breast cancer (HR = 0.92, 95% CI = 0.71 to 1.19) or death from all causes (HR = 0.83, 95% CI = 0.68 to 1.02). Analyses stratified by stage and other prognostic factors yielded similar results, except for an increased risk of breast cancer death among women with low density (BI-RADS 1) who were either obese (HR = 2.02, 95% CI = 1.37 to 2.97) or had tumors of at least 2.0 cm (HR = 1.55, 95% CI = 1.14 to 2.09).


CONCLUSIONS
High mammographic breast density was not associated with risk of death from breast cancer or death from any cause after accounting for other patient and tumor characteristics. Thus, risk factors for the development of breast cancer may not necessarily be the same as factors influencing the risk of death after breast cancer has developed.
Hormonal and Reproductive Epidemiology Branch, National Cancer Institute, National Institutes of Health, Rockville, MD, USA. gierachg@mail.nih.gov
Gretchen L
GL
Gierach
Laura
L
Ichikawa
Karla
K
Kerlikowske
Louise A
LA
Brinton
Ghada N
GN
Farhat
Pamela M
PM
Vacek
Donald L
DL
Weaver
Catherine
C
Schairer
Stephen H
SH
Taplin
Mark E
ME
Sherman
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008327:Mammography; D008875:Middle Aged; D011159:Population Surveillance; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D016019:Survival Analysis; D014481:United States / Q000453:epidemiology