Examples of these resistance associated mutations include KRAS, NRAS, MET, ERBB2, FLT3, EGFR and MAP2K1 for resistance to EGFR blockade in colorectal cancer [30], mutations in the estrogen receptor in breast cancer patients that progressed on aromatase inhibitors [33], alterations affecting the androgen receptor in prostate cancer patients who acquired resistance to anti-androgen therapy [34], and the T790M mutation in NSCLC patients that progressed on erlotinib [32]. This evidence concerns the gene ERBB2 and breast cancer.