Background: Triple-negative breast cancer (TNBC), characterized by the lack of expression of estrogenreceptor, progesterone receptor and human epidermal growth factor receptor-2, is typically associated with apoor prognosis. The majority of TNBCs show the expression of basal markers on gene expression profiling andmost authors accept TNBC as basal-like (BL) breast cancer. However, a smaller fraction lacks a BL phenotypedespite being TNBC. The literature is silent on non-basal-like (NBL) type of TNBC. The present study wasaimed at defining behavioral differences between BL and NBL phenotypes.
Objectives: i) Identify the TNBCsand categorize them into BL and NBL breast cancer. ii) Examine the behavioral differences between twosubtypes. iii) Observe the pattern of treatment failure among TNBCs. Materials and
Methods: All TNBC casesduring January 2009-December 2010 were retrieved. The subjects fitting the inclusion criteria of study weredifferentiated into BL and NBL phenotypes using surrogate immunohistochemistry with three basal markers34βE12, c-Kit and EGFR as per the algorithm defined by Nielsen et al. The detailed data of subjects werecollated from clinical records. The comparison of clinicopathological features between two subgroups was doneusing statistical analyses. The pattern of treatment failure along with its association with prognostic factorswas assessed.
Results: TNBC constituted 18% of breast cancer cases considered in the study. The BL and NBLsubtypes accounted for 81% and 19% respectively of the TNBC group. No statistically significant associationwas seen between prognostic parameters and two phenotypes. Among patients with treatment failure, 19% werewith BL and 15% were with NBL phenotype. The mean disease free survival (DFS) in groups BL and NBL was30.0 and 37.9 months respectively, while mean overall survival (OS) was 31.93 and 38.5 months respectively.Treatment failure was significantly associated with stage (p=.023) among prognostic factors.
Conclusions: Diseasestage at presentation is an important prognostic factor influencing the treatment failure and survival amongTNBCs. Increasing tumor size is related to lymph node positivity. BL tumors have a more aggressive clinicalcourse than that of NBL as shown by shorter DFS and OS, despite having no statistically significant differencebetween prognostic parameters. New therapeutic alternatives should be explored for patients with this subtypeof breast cancer.