Prevalence of the Triple-Negative Phenotype in Mexican Patients with Breast Cancer Treated in Private Practice

Background: Identifying the biological profile of breast cancer is fundamental to predict the response to various treatments and for prognosis. The aim of this study was to determine the triple-negative breast cancer prevalence in patients treated in private practice in Mexico. Methods: The study was performed using Mexican patients older than 18 years and had a histopathological diagnosis of breast adenocarcinoma and immunohistochemical studies for estrogen, progesterone, and HER2/Neu receptors, according to validated standards. Results: A total of 1,989 patients with a mean age of 52.9 ± 13.4 (23–93) years and a tumor size of 2.72 ± 1.12 cm were evaluated. The TNBC biological subtype was observed in 17.3%, HER2/Neu overexpression in 22.6%, and the presence of positive hormonal receptors (estrogen and/or progesterone) in 60.1% of the cases. An association was found between the TNBC type and the degree of differentiation (P<0.01), p53 overexpression (P<0.01, OR=1.84, 95% CI 1.35–2.52), proliferation index (P<0.01, OR=1.83, 95% CI 1.44–2.34), and tumor size (P<0.01). TNBC patients were younger (P<0.01) and lymph node involvement was more common in these patients (P<0.01, OR=4.57, 95% CI 3.53–5.90). Conclusions: TNBC is a highly aggressive tumor with a lower prevalence in women treated in private practice than in patients treated through the Seguro Popular, probably as a consequence of faster detection and opportune treatment.