However, in the cetuximab arm of the OPUS and CRYSTAL trials, the ORR and PFS of patients with KRAS mutant tumors were much worse (ORR, 26.0 and 31.3% respectively; PFS, 5.5 and 7.4 months, respectively) than patients with no tumor mutations in our study [20, 21]. The gene discussed is KRAS; the disease is neoplasm.