Prognosis of breast cancer molecular subtypes in routine clinical care: A large prospective cohort study

Background: In Germany, most breast cancer patients are treated in specialized breast cancer units (BCU), which are certified, and routinely monitored. Herein, we evaluate up-to-date oncological outcome of breast cancer (BC) molecular subtypes in routine clinical care of a specialized BCU. Methods: The study was a prospectively single-center cohort study of 4102 female cases with primary, unilateral, non-metastatic breast cancer treated between 01 January 2003 and 31 December 2012. The five routinely used molecular subtypes (Luminal A-like, Luminal B/HER2 negative-like, Luminal B/HER2 positive-like, HER2-type, Triple negative) were analyzed. The median follow-up time of the whole cohort was 55 months. We calculated estimates for local control rate (LCR), disease-free survival (DFS), distant disease-free survival (DDFS), overall survival (OS), and relative overall survival (ROS). Results: Luminal A-like tumors were the most frequent (44.7%) and showed the best outcome with LCR of 99.1% (95% CI 98.5; 99.7), OS of 95.1% (95% CI 93.7; 96.5), and ROS of 100.0% (95% CI 98.5; 101.5). Triple negative tumors (12.3%) presented the poorest outcome with LCR of 89.6% (95% CI 85.8; 93.4), OS of 78.5% (95% CI 73.8; 83.3), and ROS of 80.1% (95% CI 73.8; 83.2). Conclusions: Patients with a favorable subtype can expect an OS above 95% and an LCR of almost 100% over 5 years. On the other hand the outcome of patients with HER2 and Triple negative subtypes remains poor, thus necessitating more intensified research and care