As for trastuzumab, one variant within the FCGR2A gene (rs1801274-G), which is associated with decreased efficacy (LOE 2B), and one variant within the ERBB2 gene, which is implicated in cardiomyopathy development (LOE 3), were underrepresented in FVG population suggesting an higher therapeutic index of this drug in our population as compared to that expected in the overall European population. This evidence concerns the gene ERBB2 and cardiomyopathy.