title: Absence of the common Insulin-like growth factor-1 19-repeat allele is associated with early age at breast cancer diagnosis in multiparous women.
abstract: 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-1 (IGF-1) levels. Absence of the common IGF1 19 cytosine-adenine (CA)-repeat allele (IGF1-19/-19) inverts the effect of several non-genetic factors on breast cancer risk but the interaction between IGF1-19/-19 and multiparity on breast cancer risk is unknown. As IGF1-19/-19, multiparity and early-onset breast cancer are more common in black than in white women, we aimed to study whether multiparity combined with IGF1-19/-19 increases the risk of early-onset breast cancer. Four hundred and three breast cancer patients diagnosed in Lund, Sweden, at age 25-99 years were genotyped for the IGF1 CA-repeat length using fragment analysis. Overall, 12.9% carried the IGF1-19/-19 genotype. There was a highly significant interaction between multiparity and IGF1-19/-19 on age at breast cancer diagnosis (P=0.007). Among IGF1-19/-19 patients, multiparity was associated with a 9.2 year earlier age at diagnosis compared with uniparity or nulliparity (P=0.006). Multiparity combined with IGF1-19/-19 was associated with an early age at breast cancer diagnosis. If confirmed, IGF1-19/-19 may help identify a subgroup of women for earlier breast cancer screening.
authors.affiliation: Department of Oncology, Clinical Sciences, Lund University, SE-221 85 Lund, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Bågeman
authors.forename: C
authors.initials: C
authors.lastname: Ingvar
authors.forename: C
authors.initials: C
authors.lastname: Rose
authors.forename: H
authors.initials: H
authors.lastname: Jernström
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D001943:Breast Neoplasms / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008875:Middle Aged; D010298:Parity; D016133:Polymerase Chain Reaction; D011247:Pregnancy
chemical_list: D007334:Insulin-Like Growth Factor I