IGF1 and cancer: Thus, for example, cancer prevention trials (McTiernan, 2003) are currently being designed to modulate circulating IGF-I and IGFBP-3 as biomarkers of cancer risk, and paradoxical results may be predicted for nonsmokers vs smokers – an increase in serum IGF-I levels after smoking cessation may simply reflect peptide normalisation rather than represent a prediction of increased cancer risk.