Association between Molecular Subtypes and Survival in Patients with Breast Cancer

Background : Aim of this study is to classify intrinsic subtypes and evaluate the differences in clinical/pathological characteristics and survival outcomes among the molecular types. Patients and Methods : Breast cancer subtypes were classified according to the 2013 St. Gallen Consensus. Five molecular subtypes were determined, Luminal A, Luminal B-like HER2 negative, Luminal B-like HER2 positive, HER2 positive, and triple negative. Data was obtained from the records of patients with invasive breast cancer retrospectively. The differences in clinical/pathological parameters, overall survival and disease-free survival among the molecular subtypes were analyzed. The Kaplan-Meier method, log-rank test and Cox regression tests were used to compare groups. Results : The median follow-up period is 48 months. The Luminal B-HER2 negative was the most prevalent type (26.6%). Patient demographics, tumor characteristics and survival data were analyzed. The Luminal A and Luminal B-HER2 negative subtypes had significantly higher overall survival and disease-free survival rates. Multivariate Cox analysis revealed that tumor stage, more than 3 positive axillary lymph node involvement, and breast cancer subtype as significant factors for overall survival and disease-free survival ( p<0.05 ). Triple Negative subtype had a higher relative hazard of local recurrence and distant metastasis (HR=2.69, 95% CI=1.47; 4.95). Conclusions : Breast cancer subtype has significant impact on overall survival and disease-free survival rates. While Luminal A and luminal B HER2 negative subtypes have better outcome, triple negative and HER2- subtypes remain poor.