OBJECTIVES:  To compare budget requirements for 1^st line treatment of metastatic Colorectal Cancer (mCRC) patients with cetuximab or bevacizumab plus FOLFIRI/FOLFOX (CT) or CT alone. METHODS:  A budget impact model was developed from private payer perspective in a 5-year time horizon (2017-2021). mCRC incidence data from National Cancer Institute was adjusted based on median population growth. Drug acquisition costs were considered and prices, in Brazilian Real (BRL), were derived from official drug list price. Base scenario considered no RAS testing and all patients receiving bevacizumab+CT. Alternative scenario considered RAS testing in which RAS wild-type (wt) patients are treated with cetuximab+CT and RAS mutated (mut) receive CT alone. RESULTS:  RAS screening is mandatory for HMOs since January 2016 in Brazil. Before that, normally 1^st line treatment would be bevacizumab+CT as cetuximab+CT is registered to treat only mCRC RASwt patients. In 5 years, approximately 9,000 patients will be diagnosed with mCRC in Brazil. If bevacizumab+CT is given to all patients regardless of their RAS status, more than 2,06 billion BRL will be spent in 5 years (412 million BRL per year, approximately). If patients are tested and combination treatment of cetuximab+CT is given only to RASwt subset of patients, approximately 1,60 billion BRL will be spent in 5 years (321 million BRL per year, on average). RASmt mCRC patients could receive CT alone in 1^stline to further rational resource utilization as bevacizumab+CT failed to show superiority to CT alone in many clinical trials. CONCLUSIONS:  Biomarker selection of RASwt subgroup, which actually have the greatest potential to benefit from cetuximab+CT, allows rational resource utilization, generating savings of 454.7 million BRL to HMOs in 5-year time. Cetuximab has State tax exemption in Brazil, but even if bevacizumab is granted with such incentive there is still a saving favoring cetuximab.