Evidence obtained by Kirkham et al., 2022 [285], in a prospective study of 94 HER2-positive breast cancer patients, showed statistically significant higher levels of MMP2 in patients treated with 5-FU, epirubicin, cyclophosphamide (FEC) prior to trastuzumab treatment (234 ± 37 vs. 191 ± 45 ng/mL, p < 0.001, respectively). The gene discussed is ERBB2; the disease is breast cancer.