Remarkably, DFT1 cell lines show significantly greater sensitivity to Afatinib than a panel of ERBB2-amplified human breast cancer cell lines (Figure 5E; geometric mean DFT1 IC50: 9.8 nM, geometric mean ERBB2+ Breast cancer cell lines IC50: 314.9 nM; p = 0.000516, Wilcoxon rank-sum test). This evidence concerns the gene ERBB2 and breast cancer.