Among the clinical and molecular factors considered critical for guiding anti-EGFR therapy, tumor sidedness (as anti-EGFR agents demonstrate greater efficacy in left-sided tumors) and the mutational statuses of KRAS (Kirsten rat sarcoma viral oncogene homolog), NRAS (neuroblastoma RAS viral oncogene homolog), and BRAF (v-raf murine sarcoma viral oncogene homolog B) are paramount. The gene discussed is KRAS; the disease is neoplasm.