P. Stattin et al., Plasma insulin-like growth factor-I, insulin-like growth factor-binding proteins, and prostate cancer risk: a prospective study, J NAT CANC, 92(23), 2000, pp. 1910-1917
Background: Recent studies have suggested that men with elevated plasma lev
els of insulin-like growth factor-I (IGF-I) may have an increased risk of p
rostate cancer. Furthermore, IGF-binding proteins (IGFBPs) and insulin can
modulate the activity of IGF-I, In this study, we sought to determine the r
ole of IGF-I as well as IGFBPs-1, -2, and -3 and insulin as possible etiolo
gic factors for prostate cancer. Methods: We conducted a nested case-contro
l study within the Northern Sweden Health and Disease Cohort Study. We meas
ured levels of IGF-I, IGFBP-1, IGFBP-2, IGFBP-3, and insulin in plasma samp
les from 149 men who had a diagnosis of prostate cancer between I month and
10 Sears after blood collection and among 298 control men. All statistical
tests are two-sided. Results: Case subjects had statistically significantl
y higher mean levels of IGF-I than control subjects (229 ng/mL; 95% confide
nce interval [CT] = 218-240 ng/mL] versus 214 ng/mL [95% CI = 208-221 ng/mL
]; P = .02) and IGFBP-3 (2611 ng/mL [95% CI = 2518-2704 ng/mL] versus 2498
ng/mL [95% CI = 2437-2560 ng/mL]; P = .04). Conditional logistic regression
analyses showed increases in prostate cancer risk with rising levels of IG
F-I (P-for trend = .02) and IGFBP-3 (P-for trend = .03). In case subjects y
ounger than 59 years at the time of blood collection, the risk associated w
ith increased IGF-I was higher (P-for trend = .01), whereas the risk associ
ated with increased IGFBP-3 was lower (P-for trend = .44) than the correspo
nding risks in the full cohort. Prostate cancer risk was not associated wit
h levels of IGFBP-1, IGFBP-2, or insulin. Conclusions: Prostate cancer risk
is increased in men with elevated plasma IGF-I, This association was parti
cularly strong in younger men in this study, suggesting that circulating IG
F-I mag be specifically involved in the early pathogenesis of prostate canc
er.