LAUSR

Micro‐Abstract This was a multicenter retrospective cohort study comparing the patterns of care and clinical outcomes of 416 HER2‐positive metastatic breast cancer patients with de novo or recurrent disease undergoing first‐line trastuzumab‐based therapy. Patients with de novo disease showed significantly better survival outcomes than those with recurrent disease. Surgery of the primary breast tumor might play a role in this population. Background: The aim of the study was to compare the patterns of care and clinical outcomes of HER2‐positive metastatic breast cancer (MBC) patients with de novo or recurrent disease who underwent first‐line trastuzumab‐based therapy. Patients and Methods: This was a multicenter retrospective cohort study including consecutive patients with HER2‐positive MBC who received first‐line trastuzumab‐based therapy. Analyses on treatment response and effectiveness were conducted according to type of metastatic presentation (ie, de novo vs. recurrent disease). Exploratory analyses were used to evaluate whether the use of surgery of the primary tumor in the de novo cohort influenced patients' survival. Results: From January 2000 to December 2013, 416 patients were included in the study, 113 (27.2%) presented with de novo MBC and 303 (72.8%) with recurrent disease. Compared with patients in the recurrence cohort, those in the de novo cohort had worse baseline characteristics, received more aggressive first‐line treatments, and showed better survival, with an adjusted hazard ratio (HR) for progression‐free survival (PFS) of 0.65 (95% confidence interval [CI], 0.43‐0.97; P = .035) and for overall survival (OS) of 0.53 (95% CI, 0.30‐0.95; P = .034). In the de novo cohort, the 54 patients (47.8%) who underwent surgery of the primary tumor had significantly better PFS (adjusted HR, 0.44; 95% CI, 0.26‐0.72; P = .001) and OS (adjusted HR, 0.49; 95% CI, 0.26‐0.93; P = .029) than those who did not undergo surgery. Conclusion: 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.