Background:Classification of breast cancers into molecular subtypes may be important for the proper selection of therapy for patients with early breast cancer. Previous analyses had shown that breast cancer subtypes have distinct clinical outcome (Sorlie, PNAS, 2001; Esserman, BCRT, 2011). Herein, we analyze using MammaPrint together with an 80-gene molecular subtyping profile (BluePrint) the response to neo-adjuvant chemotherapy and long term outcomes.
Methods:This study was carried out on data from 144 patients from the I-SPY I trial; 232 patients from biomarker discovery program at MD Anderson (133 and 99 respectively; Hess, 2006, JCO; Iwamoto, 2011, BCRT); and 68 patients from City of Hope (Somlo, ASCO, 2010). All patients were treated in the neo-adjuvant setting with standard chemotherapy. MammaPrint and BluePrint were determined on 44K Agilent arrays run at Agendia or available through the I-SPY 1 data portal, or from Affymetrix U133A arrays. MammaPrint and BluePrint resulted in 4 distinct molecular groups: Luminal A (MammaPrint Low-risk/Luminal-type), Luminal B (MammaPrint High-risk/Luminal-type), Basal-type and HER2-type.
Results:The overall pCR of this patient cohort was 22% but differed substantially among the subgroups. pCR was observed in 5% of the Luminal-A samples and 10% of Luminal-B, in 39% of the HER2-type samples and in 33% of the Basal-type samples. Patients with Basal-type tumors had a 5-year DFS of 71%; HER2-type had a 5-year DFS of 67%(n=71); 69% in HER2-type subgroup not treated with HER2-targeted therapy (n=45); Luminal-B type had a 5-year DFS of 77% and Luminal-A type showed 5-year DFS of 95%.
Conclusions:We observed marked differences in response and DFS to neo-adjuvant treatment in groups stratified by MammaPrint and BluePrint. These findings confirm differences in chemotherapy response among molecular subgroups and indicate that the BluePrint and MP profile used for this analysis helps to further establish a clinical correlation between molecular subtyping and treatment outcomes.