Abstract
The goal of this study is to characterize the genomic and immune profiles of metaplastic breast cancer (MpBC) and identify the association with survival through an analysis of archived tumor tissue. A next-generation sequencing-based mutational assay (Onco-48) was performed for 21 MpBC patients. Clinicopathologic characteristics were captured, including relapse free survival (RFS) and overall survival (OS). Immunohistochemistry (IHC) for CD3, CD4, CD8, and programmed death-ligand 1 (PD-L1) was also performed. Recurrence free survival (RFS) at 5 years was 57% (95% CI 0.34–0.75) and overall survival (OS) at 5 years was 66% (95% CI 0.41–0.82). The most commonly altered genes were TP53 (68.4%, 13/19), PIK3CA (42.1%, 8/19), and PTEN (15.8%, 3/19. For patients with PIK3CA mutations, RFS and OS were significantly worse than for those without (HR 5.6, 95% CI 1.33–23.1 and HR 8.0, 95% CI 1.53–41.7, respectively). Cox regression estimated that PD-L1 expression was associated with worse RFS and OS (HR 1.08, 95% CI 1.01–1.16 and HR 1.05, 95% CI 1.00–1.11, respectively, for an absolute increase in PD-L1 expression of 1%). In conclusion, PIK3CA mutation and PD-L1 expression confer poor prognosis in this cohort of patients with MpBC.
Highlights
Metaplastic breast cancer (MpBC) is a rare malignancy which accounts for 0.05–5% of all breast cancers [1, 2]
Twenty-one eligible MpBC patients with survival data were included in this analysis
Chemotherapy remains the treatment of choice for MpBC and the prognosis is extremely poor with a median overall survival of 8 months in patients with metastatic MpBC [18, 19]
Summary
Metaplastic breast cancer (MpBC) is a rare malignancy which accounts for 0.05–5% of all breast cancers [1, 2]. MpBC is defined by differentiation of the neoplastic epithelium to a nonglandular component, typically either squamous or mesenchymal (e.g. spindle cell, osseous, or chondroid). These cancers are subdivided into groups according to the 2012 WHO Classification of Tumors of the Breast: squamous cell carcinoma, spindle cell carcinoma, mixed squamous and spindle cell carcinoma, spindle cell and mesenchymal, or mesenchymal [3]. Hope Pathology Core and Biostatistics Core supported by the National Cancer Institute of the National Institutes of Health (P30CA033572).
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