Undoubtedly, through the introduction of a new generation of effective agents with safer profiles in the last 20 years (e.g., endocrine therapy: third-generation aromatase inhibitors, fulvestrant; chemotherapy: taxanes, capecitabine, liposomal doxorubicin, gemcitabine, vinorelbine; immunotherapy: trastuzumab) and of course, through considerable advances in supportive care, longer survival times could be achieved, which in turn allows application of chronic disease treatment concepts in metastatic BC. Here, CYP19A1 is linked to breast cancer.