Neoadjuvant treatment and survival outcomes by pathologic complete response in HER2-negative early breast cancers.

Background: The benefit of pathologic complete response (pCR) in early breast cancer (eBC) is not well described in the real-world setting. This study used the nationwide Flatiron Health electronic health record-derived deidentified database to describe treatment patterns and survival outcomes by pCR status after neoadjuvant therapy (NAT) in women with triple-negative or HR+ /HER2- eBC. Materials & methods: Observational cohort study analyzing women with eBC who started NAT between 2011 and 2018. Results: 496 women were included in the study; of those, 16.1% achieved pCR, of which 35.7% were triple-negative and 6.1% were HR+ /HER2- eBC. More women with triple-negative eBC (95.2%) were exclusively treated with chemotherapy-based NAT versus HR+ /HER2- eBC (56.1%). In multivariate analyses from NAT start, not achieving pCR was associated with increased risk of death and progression. Conclusion: pCR status may be a reliable prognostic indicator for survival in these eBC subtypes in the real-world setting.