Time trends in real-world treatment patterns and survival in patients diagnosed with de novo HER2+ metastatic breast cancer: an analysis of the SONABRE registry.

PURPOSE: The aim was to determine whether the real-world first-line progression-free survival (PFS) of patients diagnosed with de novo human epidermal growth factor receptor 2 positive (HER2+) advanced breast cancer (ABC) has improved since the introduction of pertuzumab in 2013. In addition to PFS, we aimed to determine differences in overall survival (OS) and the use of systemic and locoregional therapies.

METHODS: Included were patients systemically treated for de novo HER2+ ABC in ten hospitals in 2008-2017 from the SONABRE Registry (NCT-03577197). First-line PFS and OS in 2013-2017 versus 2008-2012 was determined using Kaplan-Meier analyses and multivariable Cox proportional hazards modelling. First-given systemic therapy and the use of locoregional therapy within the first year following diagnosis were determined per period of diagnosis.

RESULTS: Median and five-year PFS were 26.6 months and 24% in 2013-2017 (n = 85) versus 14.5 months and 10% in 2008-2012 (n = 81) (adjusted HR = 0.65, 95%CI:0.45-0.94). Median and five-year OS were 61.2 months and 51% in 2013-2017 versus 26.1 months and 28% in 2008-2012 (adjusted HR = 0.55, 95%CI:0.37-0.81). Of patients diagnosed in 2013-2017 versus 2008-2012, 84% versus 60% received HER2-targeted therapy and 59% versus 0% pertuzumab-based therapy as first-given therapy. Respectively, 27% and 23% of patients underwent locoregional breast surgery, and 6% and 7% surgery of a metastatic site during the first year following diagnosis.

CONCLUSION: The prognosis of patients with de novo HER2 + ABC has improved considerably. Since 2013 one in four patients were alive and free from progression on first-given therapy for at least five years.