Several studies have suggested that anthracyclines such as doxorubicin have a steep dose–response curve in HER2-positive breast cancer (Muss et al, 1994), but a supposed sensitivity to anthracyclines has not been confirmed invariably (Paik et al, 1998; Thor et al, 1998; Vincent-Salomon et al, 2000). The gene discussed is ERBB2; the disease is breast carcinoma.