IGF1 and breast cancer: Although previous studies showed an association between high serum concentrations of IGF-I and risk of prostate, colorectal, and breast cancers (Rowlands et al, 2009; Chan et al, 1998, 2002; Ma et al, 1999; Yu et al, 2002; Renehan et al, 2004), subsequent studies have found low IGF-I levels to be associated with an increased risk for brain and kidney cancer (Lonn et al, 2007; Major et al, 2010).