The IGF system is associated with both breast cancer risk (Renehan et al, 2004; Fletcher et al, 2005; Rinaldi et al, 2006) and postnadir growth (Albertsson-Wikland et al, 1998; Ogilvy-Stuart et al, 1998; Hikino et al, 2001; Skalkidou et al, 2003), and could therefore plausibly explain the association of postnadir growth with this risk. This evidence concerns the gene IGF1 and breast carcinoma.