Estrogen metabolites and the risk of breast cancer in older women.
BACKGROUND
Women who metabolize a large proportion of their estrogen via the 16alpha hydroxylation pathway could be at a higher risk of breast cancer. The objective of this study was to test the hypothesis that serum concentrations of 2-hydroxyestrone (2-OHE1) and 16alpha-hydroxyestrone (16alpha-OHE1), as well as their ratio, predict the risk of breast cancer in older women.


METHODS
We performed a case-cohort study of 272 women with confirmed incident breast cancer and 291 controls chosen randomly from the cohort. Estrogen metabolites were measured in serum collected at the baseline examination and stored at -120 degrees C. Incident breast cancers were confirmed by medical records and pathology reports during an average follow-up of 8.7 years.


RESULTS
Mean concentrations of 2-OHE1 and 16alpha-OHE1, adjusted for age and body mass index, were 3% to 4% higher in cases compared with controls: 2-OHE1 was 176 pg/mL and 169 pg/mL and 16alpha-OHE1 was 233 pg/mL and 226 pg/mL in cases and controls, respectively. There was, however, no difference in the ratio of 2-OHE1 to 16alpha-OHE1. The risk of breast cancer in women with the highest quartile of this ratio compared with those in the lowest quartile was 1.17 (95% confidence interval = 0.73-1.87).


CONCLUSIONS
The study results do not support the hypothesis that the ratio of 2-OHE1 to 16alpha-OHE1 predicts breast cancer risk.
Cauley
Jane A
JA
Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. jcauley@pitt.edu
Zmuda
Joseph M
JM
Danielson
Michelle E
ME
Ljung
Britt-Marie
BM
Bauer
Douglas C
DC
Cummings
Steven R
SR
Kuller
Lewis H
LH
D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology / Q000378:metabolism*; D016022:Case-Control Studies; D015331:Cohort Studies; D004967:Estrogens / Q000097:blood / Q000378:metabolism*; D005260:Female; D006801:Humans; D006894:Hydroxyestrones / Q000097:blood; D012307:Risk Factors; D039181:Steroid 16-alpha-Hydroxylase / Q000097:blood; D011795:Surveys and Questionnaires
D004967:Estrogens; D006894:Hydroxyestrones; C026702:16-hydroxyestrone; D039181:Steroid 16-alpha-Hydroxylase; C024980:2-hydroxyestrone