The 10 most studied cancer cell gene variants were TP53 and cisplatin/5-fluorouracil/paclitaxel response, ERBB2 (HER2/neu) and anthracyclines/trastuzumab response, EGFR and gefitinib response, and RAS, FLT3, ABCB1, BCL2 and t(9;22) and other karyotype and cytogenetic mutations and response to a variety of combination chemotherapy regimens. The gene discussed is EGFR; the disease is cancer.