Can patients with metastatic breast cancer be cured after introduction of newer and more effective agents?

Unlike early stage breast cancer, metastatic breast cancer (MBC) is generally considered incurable except for a small number of patients with oligometastatic disease. The goal of treatment of MBC should be the prolongation of life and improvement of symptoms and quality of life. The prognoses of patients with MBC, however, have been improved with the introduction of newer, more effective agents. Therefore, the clinical question arises whether MBC patients can be cured with these new therapeutic agents. However, there are a couple of problems in tackling this question, including the duration of follow-up and the presence of strong adjuvant therapy. Firstly, most trials in MBC have a relatively short follow-up; long-term surveillance (>3-5 years) is exceptional, so little is known about the definitive outcome and the exact proportion of long-term survivors. Secondly, most of the patients have received pre- or postoperative adjuvant therapy. The cancer cells at metastatic sites are considered to be relatively resistant to the agents used in metastatic settings. Promisingly, a number of novel therapeutic agents including antibody-drug conjugates, irreversible small molecule HER2-tyrosine inhibitors, and HER2 dimerization inhibitors show promise in the treatment of HER2-overexpressing MBC, as well as PARP-1 [poly(ADP-ribose) polymerase-1] inhibitors for triple-negative breast cancer.