Investigating the same six xenografts’ response to each of three therapies: cisplatin, cetuximab, and radiation, provided a controlled environment in which to relate tumor responses to the pre- and posttreatment expression of five potential predictive biomarkers: EGFR, pEGFR, pAkt, pERK, and ERCC1. The gene discussed is ERCC1; the disease is neoplasm.