The invention relates to methods of treating of subject that has breast cancer or is at risk of having said cancer, comprising administering to the subject in need thereof a combination of a therapeutically effective amount of an ErbB-2/ErbB-3 bispecific antibody and a therapeutically effective amount of an endocrine therapy drug, wherein the bispecific antibody has an antigen binding site that can bind an extra-cellular part of ErbB-2 and an antigen binding site that can bind an extra-cellular part of ErbB-3； and to means for said method.
