Archived plasma samples collected before and after trastuzumab treatment at various fixed time points from 15 HER2+ patients with or without cardiotoxicity, recently collected plasma samples from 79 breast cancer patients (40 HER2+, 39 HER2-), and 46 healthy donors were analyzed for cMLC-1 levels using an enzyme-linked immunosorbent assay (ELISA). This evidence concerns the gene ERBB2 and breast carcinoma.