In NSCLC xenografts metformin given orally (in drinking water) at a dose of 250mg/kg/day enhanced the activation of ATM - AMPK - p53/p21cip1 axis induced by RT, inhibited tumor growth and enhanced the cytotoxicity of RT, inhibited angiogenesis and enhanced the induction of apoptotic markers. This evidence concerns the gene TP53 and neoplasm.