Abstract PS1-09-13: Development of Staging Guidelines for Metastatic Breast Cancer: Which method is best?

Abstract Background: Breast cancer staging is a foundational component for determining prognosis, and multiple methods have been used to create staging guidelines. However, it remains unclear which statistical approach is best. As such, we sought to compare 3 methods for developing staging guidelines, using de novo metastatic breast cancer (dnMBC) as an example. Methods: Patients with dnMBC in the National Cancer Database (2010-2022) were identified (N=48,832). Variables used for staging included clinical T-category, grade, ER, PR, HER2, histology, bone-only metastases, brain-only metastases, visceral metastases, and number of metastatic sites. Stage groups were assigned based on 3-year overall survival (OS) rates: stage group IVA >70%, IVB 50-70%, IVC 25-