BACKGROUND:
This study was conducted to explore the effect of known
risk factors, focusing on
risk factors including age at
menarche, age at
menopause, number of
children,
family history of
breast cancer, and age at
first birth according to
breast density, in consideration of interaction among East-
Asian women.
METHODS:
Case-control study with 2,123 cases and 2,121 controls with
mammographic density was conducted. Using the mammographic
film,
breast density was measured using
Breast Imaging-
Reporting and Data System. To identify the
association of selected reproductive factors including age at
menarche, age at
menopause, number of
children,
family history of
breast cancer, and age at
first birth according to
breast density, stratified
analysis was conducted according to
breast density groups and interaction effects was assessed. The results were presented with adjusted OR and 95% CIs.
RESULTS:
Significant interaction effect between age at
first birth and
breast density on
breast cancer (P = 0.048) was observed.
Women with age at
first birth ≥ 28 years old showed increased
breast cancer risk in extremely dense
breast group (≥ 75%) (OR = 1.627, 95% CI = 1.190–2.226). However,
women with fatty
breast (< 50%) and heterogeneously dense
breast (50%–75%) did not show an increased
association. Age at
menarche, age at
menopause, number of
children, and
family history of
breast cancer did not show significant interaction with
breast cancer and
similar risk patterns were observed.
CONCLUSIONS:
Age at
first birth showed significant interaction with
breast density on
breast cancer risk. Further studies considering biologically plausable model between exposure, intermediate outcomes and
breast cancer risk with prospective design need to be undertaken in
East Asian women.