Histopathological Patterns and Outcomes of Triple-Positive Versus Triple-Negative Breast Cancer: A Retrospective Study at a Tertiary Cancer Center.

Background One of the leading causes of cancer-related deaths in females under 45 years old is breast cancer (BC). The definition of triple-negative breast cancer (TNBC) is the lack of expression of estrogen receptors (ERs) as well as progesterone receptors (PRs) and Erb-B2 receptor tyrosine kinase 2 (HER2) gene amplification. Triple-positive breast cancer (TPBC), on the other hand, is defined as tumors expressing a high level of ER, PR, and HER2 receptors. This study aims to assess the phenotypes of TNBC and TPBC by comparing their individual clinical behavior patterns and prognosis throughout the course of the disease in a tertiary cancer center in the Kingdom of Saudi Arabia (KSA). Methods Our study is a retrospective study using electronic medical records (EMRs) to identify all female patients diagnosed with BC using the International Classification of Diseases-10 (ICD-10) codes (between C50 and C50.9). About 1209 cases with primary BC female patients were recognized based on histopathology reports. Further subclassification into TPBC and TNBC was performed. Statistical analysis was performed using Rv3.6.2 (R Studio, version 3.5.2, Boston, MA, USA). The descriptive data were presented as means and standard deviations (SD). Survival curves were approximated using the Kaplan-Meier method. The comparison between survival curves between both groups was achieved using the log-rank test. The multivariate model was constructed based on the identified predictors using univariate analysis. Results Univariate analysis of overall survival (OS) showed that mortality was higher in TNBC compared to TPBC (HR = 2.82, P-value <0.05). However, in a multivariate analysis, molecular subtypes did not show a significant effect on OS with a P-value of 0.94. We found that age at diagnosis has been associated with a 4% increase in mortality risk with a yearly rise in age. Conclusion In this limited retrospective cohort study, we found that TNBC may not be associated with a higher risk of death than TPBC. However, other factors, including age at diagnosis, surgical intervention, and lymphovascular invasion (LVI), have been observed to increase the risk of mortality. On the other hand, patients with TNBC were found to have a worse prognosis in terms of local recurrence. This information cannot be generalized to all patients with BC given the limitations of this study. Further, larger cohorts are needed to explore biological and treatment-related outcomes in patients with TNBC and TPBC.