At the molecular level, some of the biological factors proposed thus far as potential prognostic factors in osteosarcoma are p15, p16 (Nielsen et al, 1998; Maitra et al, 2001), p53 (Park et al, 2001), Rb (Wadayama et al, 1994) and c-met (Ferracini et al, 1995; Oda et al, 2000), but these studies have mainly been performed on small populations. This evidence concerns the gene RB1 and osteosarcoma.