Triple-negative breast cancer in Thai patients: Experience in King Chulalongkorn Memorial Hospital

Abstract

Background : Triple-negative breast cancer (TNBC) is defined by the lack of expression of ER, PR and Her-2 receptors and exhibits aggressive behaviors and poor clinical outcomes. Eighty percent of TNBCs are classified as
basal-like tumor and share clinical behaviors that are consistent with this subtype of breast tumors.

Objectives : To characterize the epidemiological features of triple-negative breast cancers (TNBC) occurring in Thai patients in terms of demographics and pathological hallmarks including the expression patterns of ER, PR, Her-2, CK5/6, CK17 and EGFR as well as clinical outcomes.

Methods : In 166 TNBCs, adequate tissue samples were obtained from seventy cases, and patient/tumor characteristics as well as the survival outcomes were reviewed retrospectively.

Results : The mean age was 48.04 years (range 26 – 79 years); 89% of the tumors were invasive ductal carcinomas, and 72.4% were high-grade tumors. A high proliferative index (Ki-67 > 30%) was found in 81.4% of the samples. Positive staining for CK5/6 and CK17 were found in 51.4% and 55.7% of the tumors, respectively; 58.6% of the tumors had EGFR expression. After we analyzed the expressions of ER, HER-2, CK5/6 and EGFR to define the basal phenotype, 72.9% were categorized into the basal-like group. At a median of 67.5 months, 32.5% of the tumors
recurred and 30.1% of the patients had died. The 5-year disease-free survival and overall survival estimates were 69% and 74%, respectively. In multivariate Cox proportional hazards models, the basal-like subtype was not independently correlated with DFS or OS in TNBCs (HR 1.72, [95% CI, 0.13 - 22.96], P = 0.68; for DFS and HR 2.34, [95% CI, 0.17 - 31.75], P = 0.52 for OS).

Conclusions : TNBCs occurred at younger age in these Thai patients than in previous studies. We also demonstrated higher tumor grades, higher proliferation indices and inferior outcomes of TNBCs in Thai patients. Additionally, the presence of basal-like characteristics was not an independent predictor of the survival outcome.