Impact of St. Gallen surrogate classification for intrinsic breast cancer sub-types on disease features, recurrence, and survival in South Indian patients

Background: Breast cancer is a heterogeneous group of disease, and recently, intrinsic sub-typing on the basis of gene expression profiling is found to be a predictor of breast cancer clinical course. The St. Gallen has released surrogate classification for breast cancer sub-types depending on immunohistochemistry (IHC) markers. Aim: The aim of our study was to analyze the distribution of sub-types using IHC surrogate markers in our patient population and to assess the clinico-pathological factors in different sub-types. Materials and Methods:A total of 635 non-metastatic patients who underwent radical intend treatment from January 2011 to December 2013 were included for this retrospective analysis. A statistical analysis was done by Windows SPSS version 20. The Chi-square test was used to examine the correlations of these sub-types with clinico-pathological parameters. The Kaplan-Meier method estimates were used for survival analysis. Results: The median follow-up was 42.77 months (5 months to 112 months). Luminal B was the predominant group. Disease free survival (DFS) at 5 years was 95% in luminal A, 78% in luminal B HER-2 negative, 80% in luminal B HER-2 positive, 72% in triple negative, and 79% in HER-2/neu non-luminal. Tumor size, Ki67, T stage, N stage, and grade were significantly associated with DFS in all biological type with a P value of less than 0.05. Conclusion: Surrogate classification was successfully applied in our patient cohort. Luminal B and triple negative sub-groups were more prevalent in our patients, and this finding is at variance with published international data. Biological sub-type also emerged as an important predictor of survival.