question: Which gene(s) should be genotyped in order to prescribe the drug Cetuximab (anti-EGFR)?
answer: KRAS mutation has been unambiguously identified as a marker of resistance to cetuximab-based treatment in metastatic colorectal cancer (mCRC) patients.
  Other genes are such as EGFR, BRAF and T53 have also been suggested to be genotyped in order to evaluate the drug responsivness.