Predictive Factors of Recurrence Free Survival of Patients with Luminal Breast Cancer in Southern Sri Lanka

Abstract

Purpose: To assess the predictive factors of recurrence free survival (RFS) of luminal breast cancers in Southern Sri Lanka to bridge the existing gap in published literature on luminal breast cancers in our country. Materials and Methods: This was a bidirectional; retro prospective, cohort study. All breast cancer patients who sought the services of our immunohistochemistry (IHC) laboratory from 2006 to 2015 were included. Tissue micro arrays were constructed using the archives for the IHC analysis of Ki67, CK5/6 and EGFR. Details of ER, PR and Her2 expression were extracted from the laboratory records. Clinico-pathological data were retrieved from the records available in the laboratory, Oncology clinic and from patients. Pearson chi-square test, Kaplan-Meier model, log-rank test and Cox-regression model were used with SPSS for data analysis. Results: A total of 595 luminal breast cancers were included. Majority, were between 36–60 years of age (65.5%), Nottingham grade 2 (57.4%), TNM Stage II/III (82.0%) and had T2 tumours (53.6%). Recurrences were noted in 15.9% (n = 395, local-16.9%; distant metastasis-76.9%; second cancer-6.2%). Median follow up time was 35 months. Only 443 luminal breast cancers could be subtyped (luminal A-58.7%); luminal B Her2-negative- 22.3%; luminal B Her2-positive-19.0%). Five-year RFS of the cohort was 74.1% (luminal A-83.6%; luminal B(Her2-negative)-73.9%; luminal B(Her2-positive)-55.3%; P = 0.001). Over-expression of Her2 (P = 0.018) and CK5/6 expression (P = 0.003) had an independent effect on the RFS of the cohort. Conclusion: The three subtypes of luminal breast cancers are distinct in their recurrence free survival and tumor characteristics. Over-expression of Her2 and CK5/6 expression had an independent negative effect on the RFS of the luminal breast cancer cohort.