Roddam AW et al. (2008) Insulin-like growth factors, their binding proteins, and prostate cancer risk: analysis of individual patient data from 12 prospective studies. Ann Intern Med 149: 461–471

Some studies have indicated that levels of circulating insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) are associated with the risk of developing prostate cancer, whereas other studies have shown no such relationship. Roddam et al. have now found that high circulating levels of IGF-I are associated with a moderately raised risk of developing prostate cancer.

The authors searched PubMed, Web of Science and CancerLit for all studies that provided prospectively collected data on circulating concentrations of IGFs or IGFBPs and prostate cancer risk. The authors of these studies were invited to submit individual participant data to a central data set.

In the 3,299 patients with prostate cancer and 4,436 control individuals assessed, the risk of prostate cancer was found to increase as circulating concentrations of IGF-I increased (odds ratio [highest vs lowest quintile] 1.38; P <0.001 for trend). Elevated IGF-I concentrations were more strongly associated with low-grade disease than high-grade disease. Raised levels of IGFBP-III were also associated with increased prostate cancer risk; however, this effect was secondary to the correlation between IGFBP-III and IGF-I levels. Neither IGF-II nor IGFBP-II concentrations were associated with prostate cancer risk.

The relationship between IGF-I and prostate cancer risk could be due to the mitogenic and antiapoptotic effects of this growth factor. The authors suggest that modification of circulating IGF-I levels through dietary and lifestyle changes might reduce the risk of prostate cancer.