Outcomes of Metaplastic Breast Cancer Versus Triple-Negative Breast Cancer: A Propensity Score Matching Analysis

Abstract

Purpose: This study aims to compare the survival outcomes of metaplastic breast cancer (MPBC) with triple-negative breast cancer (TNBC) and identify prognostic factors that influence the survival outcomes of MPBC patients and TNBC patients.

Methods: Patients with nonmetastatic MPBC or TNBC were reviewed from our database. Patients' clinicopathologic and molecular features were analyzed with respect to outcomes, including disease-free survival (DFS) and overall survival (OS). Propensity score matching (PSM) with a one-to-three matching between MPBC patients and TNBC patients was performed.

Results: A total of 857 female patients (76 MPBC patients and 781 TNBC patients) were included in this study. A subgroup of triple-negative MPBC (n = 60) was matched with TNBC (n = 180) cases based on patient characteristics and treatments. Kaplan-Meier analysis indicated that the MPBC group was associated with worse OS and DFS before (P = 0.0046 both) and after (P = 0.011 and P = 0.0046, respectively) PSM. Multivariable analysis revealed that a higher T stage (T > 2) (P = 0.032) and higher lymph node stage (N3 vs. N0-2, P = 0.012) were associated with worse OS after PSM. For DFS, the MPBC group (P = 0.012), higher T stage (T > 2) (P = 0.032), and higher lymph node stage (N3 vs. N0-2, P = 0.045) were associated with worse DFS. Among the 76 MPBC patients, a higher T stage and mesenchymal differentiation were associated with worse OS (pT1/2 vs. pT3/4 and mesenchymal differentiation vs. other subtypes, P = 0.007 and P = 0.011, respectively).

Conclusions: Compared with TNBC, MPBC was associated with worse OS and DFS. Mesenchymal differentiation has a worse DFS than other subtypes of MPBC.