Plasma isoflavones and fibrocystic breast conditions and breast cancer among women in Shanghai, China.
BACKGROUND
Proliferative benign breast conditions are associated with elevated risk of breast cancer, whereas nonproliferative conditions are not strongly associated with risk. Factors acting before onset of hyperplasia might be associated with both benign conditions and breast cancer, whereas those on the proliferative disease-to-cancer pathway would be associated only with cancer. Soy isoflavone exposure may influence breast cancer risk, but little is known of its association with benign conditions.


METHODS
We examined possible relationships between plasma genistein and daidzein concentrations and risk of breast disease in women, in a breast self-examination trial in Shanghai, China, diagnosed with breast cancer (n = 196) or a benign breast condition (n = 304), and 1,002 age-matched controls with no known breast disease. Benign conditions were classified as nonproliferative (n = 131) or proliferative with or without atypia (n = 173).


RESULTS
Isoflavone concentrations were inversely associated with risk of nonproliferative and proliferative benign fibrocystic conditions, as well as with breast cancer, both with and without concomitant proliferative changes in ipsilateral noncancerous mammary epithelium (P(trend) < 0.01 for all comparisons with controls). Women in the highest quartile of plasma genistein (>76.95 ng/mL) were less likely to have breast cancer (odds ratio, 0.26; 95% confidence interval, 0.13-0.50) or benign conditions (odds ratio, 0.40; 95% confidence interval, 0.23-0.70) compared with women in the lowest quartile (<9.42 ng/mL). Observed risks for breast cancer with and without surrounding proliferative changes were not different, respectively, from observed risks for benign proliferative and nonproliferative conditions alone.


CONCLUSIONS
Isoflavone exposure was inversely associated with fibrocystic breast conditions and breast cancer, and the results suggest that effects on cancer risk occur early in carcinogenesis.
Lampe
Johanna W
JW
Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. jlampe@fhcrc.org
Nishino
Yoshikazu
Y
Ray
Roberta M
RM
Wu
Chunyuan
C
Li
Wenjin
W
Lin
Ming-Gang
MG
Gao
Dao Li
DL
Hu
Yongwei
Y
Shannon
Jackilen
J
Stalsberg
Helge
H
Porter
Peggy L
PL
Frankenfeld
Cara L
CL
Wähälä
Kristiina
K
Thomas
David B
DB
D000328:Adult; D001943:Breast Neoplasms / Q000097:blood* / Q000453:epidemiology; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D002853:Chromatography, Liquid; D004032:Diet; D005260:Female; D005348:Fibrocystic Breast Disease / Q000097:blood* / Q000453:epidemiology; D019833:Genistein / Q000097:blood*; D006801:Humans; D007529:Isoflavones / Q000097:blood*; D013058:Mass Spectrometry; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D030262:Soybean Proteins
D007529:Isoflavones; D030262:Soybean Proteins; C004742:daidzein; D019833:Genistein