Absence of the common Insulin-like growth factor-1 19-repeat allele is associated with early age at breast cancer diagnosis in multiparous women.
Multiparity decreases the risk of breast cancer in white women, whereas it is a risk factor in black women < 50 years. Early-onset breast cancer (< 50 years) has been associated with high insulin-like growth factor-I (IGF-I) levels. Absence of the common IGFI 19 cytosine-adenine ( CA)- repeat allele (IGFI-19/-19) inverts the effect of several non-genetic factors on breast cancer risk but the inter