Considering that 5-FU is widely prescribed for the treatment of solid carcinomas, like those of the gastrointestinal tract, pretreatment DPYD genotyping could be performed together with the detection of KRAS and BRAF somatic mutations in patients with colorectal cancer to predict the response to anti-EGFR monoclonal antibodies, recommended by regulatory authorities (van Krieken et al., 2008; Allegra et al., 2009; NCCN Colon Cancer Guidelines, 2011). The gene discussed is KRAS; the disease is colorectal cancer.