Prognostic value of the X-linked inhibitor of apoptosis protein for invasive ductal breast cancer with triple-negative phenotype

Molecular classification has raised new hopes of improving our understanding of breast cancer. Discovery of novel tumor markers that allow the identification of patients at higher risk for invasive ductal breast cancer with triple-negative phenotype remains a research and clinical priority. To evaluate the prognostic value of the X-linked inhibitor of apoptosis protein for invasive ductal breast cancer with triple-negative phenotype by correlating the expression of X-linked inhibitor of apoptosis protein with clinicopathologic parameters, thus determining its role in predicting tumor outcomes, 200 cases of patients with invasive ductal breast cancer, including their complete information, were obtained. Tissue microarrays were constructed; and immunohistochemical staining was performed to detect the expression of the estrogen receptor, progesterone receptor, HER2/neu, Ki-67, and X-linked inhibitor of apoptosis protein. We identified 42 cases of invasive ductal breast cancer with triple-negative phenotype. Of these, X-linked inhibitor of apoptosis protein expression was detected in 32 patients (80%). Significant correlations were found between X-linked inhibitor of apoptosis protein expression and primary tumor size (P = .027), and between X-linked inhibitor of apoptosis protein expression and Ki-67 index (P = .038). Kaplan-Meier survival analysis revealed a pattern of X-linked inhibitor of apoptosis protein expression with impaired overall and disease-free survival in patients with the disease. Most importantly, multivariate analysis also showed statistically significant worse outcomes for patients with tumors exhibiting X-linked inhibitor of apoptosis protein expression of at least 50% compared with those with X-linked inhibitor of apoptosis protein expression less than 50%. In conclusion, our results suggest that X-linked inhibitor of apoptosis protein is a novel biomarker and viable prognostic factor for invasive ductal breast cancer with triple-negative phenotype. Furthermore, the expression of X-linked inhibitor of apoptosis protein is significantly correlated with a more aggressive tumor phenotype and decreased overall and disease-free survival.