Prospective study of IGF-I, IGF-binding proteins, and breast cancer risk, in northern and southern Sweden.
OBJECTIVE
To examine the possible relationships of breast cancer risk to prediagnostic plasma levels of insulin; insulin-like growth factor-I (IGF-I); and IGF-binding proteins -1, -2, and -3.


METHODS
Within two prospective cohorts in Umeå and Malmö we measured plasma concentrations of insulin, IGF-I, and IGFBPs for a total of 513 incident breast cancer cases and 987 matched controls.


RESULTS
Globally, risk was unassociated with levels of IGF-I, IGFBP-3, or IGF-I adjusted for IGFBP-3. When breaking down the analysis by subgroups of age at blood donation, an increase in risk was observed for increasing levels of IGF-I in women aged 55 or older, in the Umeå cohort only (odds ratios of 1.00, 1.73, 1.76, 1.90; Ptrend = 0.05). This effect weakened, however, when the analysis was restricted to subjects who did not use exogenous hormones for the treatment of menopausal symptoms. Levels of IGF-I and IGFBP-3 were not related to risk in younger women, recruited before age 50, contrary to observations from previous studies. In a subcohort where blood samples had been collected after at least four hours of fasting, breast cancer risk showed no clear associations with levels of insulin, IGFBP-1, or IGFBP-2.


CONCLUSIONS
Our results do not confirm earlier findings of an association of plasma IGF-I levels with breast cancer risk especially in young women, but suggest a possible association with postmenopausal breast cancer risk, possibly among ERT/HRT users only. Our results do not support the hypothesis that elevated plasma insulin levels, and reduced levels of IGFBP-I and IGFBP-2, are associated with increased breast cancer risk.
Kaaks
Rudolf
R
Unit of Nutrition and Cancer, International Agency for Research on Cancer, Lyon, France. kaaks@iarc.fr
Lundin
Eva
E
Rinaldi
Sabina
S
Manjer
Jonas
J
Biessy
Carine
C
Söderberg
Stefan
S
Lenner
Per
P
Janzon
Lars
L
Riboli
Elio
E
Berglund
Göran
G
Hallmans
Göran
G
D000328:Adult; D000367:Age Factors; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control*; D016022:Case-Control Studies; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D007328:Insulin / Q000097:blood* / Q000494:pharmacology; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood* / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000494:pharmacology; D008875:Middle Aged; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology
D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I