Trastuzumab showed higher in vitro cytotoxicity against peripheral blood mononuclear cells carrying the CD16158V/V than CD16158V/F or CD16158F/F variants, although only one clinical study in patients with metastatic human epidermal growth factor receptor 2-positive breast cancer treated with a combination of trastuzumab and a taxane showed a correlation between the CD16158V/V phenotype and an improved objective response rate and prolonged progression-free survival [43,44]. Here, ERBB2 is linked to breast cancer.