Insulin-like growth factor (IGF)-I, IGF-II, IGF binding protein-3, and risk of colorectal cancer: a nested case-control study in the Japan Collaborative Cohort study.

Insulin-like growth factor (IGF)-I and IGF-II are important mitogen and IGF binding protein-3 (IGFBP-3) exerts opposite effects. However, the results of epidemiological studies on cancer influence are somewhat controversial, and mainly from Western countries. In the present study, we therefore examined associations of serum IGF-I, IGF-II and IGFBP-3 with colorectal cancer risk among participants in the JACC Study in Japan. After matching 3 controls to cases by sex, age, and study area, a total 101 risk sets were examined using a conditional logistic regression model adjusted for body mass index, smoking habit, alcohol consumption and family history of colorectal cancer. The odds ratios (and 95% CIs) for colorectal cancer mortality among the highest tertiles of IGF-I, IGF-II, and IGFBP-3, compared to the lowest tertiles were 1.01 (0.49-2.10), 1.02 (0.55- 1.91), and 1.22 (0.63-2.38), respectively. No linear trends were observed. The lack of any association was not altered after additional adjustment for mutual markers of IGF-I/IGF-II or IGFBP-3, 0.76 (0.34-1.71) for IGF-I, 0.66 (0.30-1.45) for IGF-II, and 1.11 (0.47-2.66) for IGFBP-3. Our prospective data thus indicated that there is no association of IGF-I, IGF-II, and IGFBP-3 with colorectal cancer risk in the Japanese population. Although these markers might be etiologically significant in relation to colorectal cancer, we did not obtain evidence supporting this hypothesis.