Novel prognostic staging system for patients with de novo metastatic breast cancer: A real-world experience.

Abstract

e13167 Background: De novo metastatic breast cancer (dnMBC) is a heterogenous disease with variable survival rates. For newly diagnosed, non-MBC, the AJCC staging system incorporates non-anatomical factors, biomarkers and grade, in addition to tumor size and nodal status to define the prognostic stage group. These variables and other disease-related factors, such as sites of metastasis, have been associated with survival in MBC. Despite this, the current staging system groups all patients with dnMBC into a single prognostic group. More tools are needed to help clinicians relay important prognostic information to patients with dnMBC. Plichta et al. [1] utilized large population data sets to develop a novel staging system for dnMBC, which successfully stratified patients into four prognostic groups (IVA-D) based on disease-related variables. In this study, we sought to validate this staging system in an independent, real-world cohort of patients with dnMBC. Methods: We used a retrospective cohort of patients with MBC who received treatment in the Koontz Center for Advanced Breast Cancer (KABCC) at St. Luke’s Cancer Institute, a community-based healthcare system in the Kansas City metro area. The KABCC is a multidisciplinary clinic dedicated solely to the care of patients with MBC. Patients with dnMBC were assigned prognostic stage IVA, IVB, IVC, and IVD according to the system developed by Plichta et al. [1]. Overall survival (OS) was compared between groups using Kaplan-Meier analysis and the log-rank test. We also performed a stratified analysis based on age at diagnosis, <60 years versus ≥60 years. Results: Ninety-seven patients with dnMBC were included in the analytic cohort. Mean age at diagnosis was 60 years, and most patients self-identified as non-Hispanic White (71.1%) or Black (22.7%). Nine patients were assigned stage IVA (9.3%), 39 stage IVB (40.2%), 32 stage IVC (33%) and 16 stage IVD (16.5%). Most stage IVA were HER2 positive (66.7%), while most stage IVD were triple-negative (56.3%). OS differed significantly between the four stage groups, with mortality rates increasing as stage increased. This was true in both the overall population (p<0.001) and when patients were stratified by age at diagnosis (both p<0.05) (Table). Conclusions: In an independent, real-world cohort of patients with dnMBC, a novel prognostic staging system that incorporates biomarkers, T-stage, grade, and sites of metastasis successfully stratified patients into four prognostic groups. Our findings help to confirm the utility of this staging system in dnMBC. [Table: see text]