Patterns of Care and Clinical Outcomes of HER2-positive Metastatic Breast Cancer Patients With Newly Diagnosed Stage IV or Recurrent Disease Undergoing First-line Trastuzumab-based Therapy: A Multicenter Retrospective Cohort Study

Patients with de novo HER2-positive MBC showed significantly better survival outcomes than those with recurrent disease. In this population, surgery of the primary breast tumor was associated with better outcomes.