Comparative prognostic analysis for triple-negative breast cancer with metaplastic and invasive ductal carcinoma

Aims Triple-negative breast cancer comprises different histological subtypes, including metaplastic breast cancer (MBC) and ductal carcinomas (IDCs). The purpose of this study was to compare triple-negative MBC (TN-MBC) with triple-negative IDC (TN-IDC) in terms of survival and predictive factors. Methods With access to the Surveillance, Epidemiology and End Result (SEER) database, a total of 19 383 patients met the eligibility criteria. Clinicopathological characteristics were compared between groups using the chi(2) test. Univariate and multivariate analyses were applied to evaluate the disease-specific survival (DSS) and overall survival (OS). Subgroup analyses summarised the hazard ratios of TN-MBC versus TN-IDC using a forest plot. Results A total of 586 patients with TN-MBC and 18 797 with TN-IDC were included in this study. Patients with TN-MBC were older and presented with larger tumour sizes, relatively rare lymph node positive disease, and had received more chemotherapy. Compared with TN-IDC, the TN-MBC group showed a significantly poorer prognosis before and after the 1: 3 matched case-control analysis. Further subgroup analysis indicated that patients with TN-MBC were older, were from specific races, and those with distant metastasis and not receiving radiotherapy had worse prognosis than patients with TN-IDC in terms of DFS and OS. Conclusion Our results showed that patients with TN-MBC had unique clinicopathological characteristics and poorer prognostic subtype compared with TN-IDC. This improves our understanding of the clinicopathological and prognostic features of this rare entity but also provides more convincing therapeutic guidelines for TN-MBC in patients with breast cancer.