PTEN loss of expression predicts cetuximab efficacy in metastatic colorectal cancer patients - Frattini, M; Saletti, P; Romagnani, E; Martin, V; Molinari, F; Ghisletta, M; Camponovo, A; Etienne, L L; Cavalli, F; Mazzucchelli, L (Br J Cance, 2007)