Molecular subtyping using MammaPrint and BluePrint as an outcome predictor in U.S. breast cancer (BC) patients.

Abstract

9 Background: Combined use of MammaPrint and a molecular subtyping profile (BluePrint) identifies disease subgroups with marked differences in long-term outcome and response to neo-adjuvant therapy (Glück SABCS2011). The aim of this study was to evaluate the prognostic value of Molecular Subtyping using MammaPrint and BluePrint in women with early stage BC treated at U.S. institutions following National Comprehensive Cancer Network (NCCN) standard guidelines. Methods: Frozen tumor samples from 180 BC patients (TI-III, N0-Ib) median age 57 years at diagnosis (range 28-89) were suitable for hybridization on full genome array. MammaPrint and BluePrint Molecular Subtypes were determined and survival for Luminal A (MammaPrint Low Risk), Luminal B (MammaPrint High Risk), HER2-type and Basal-type patients was assessed. Patients were treated either with breast conserving therapy or mastectomy with axillary lymph node dissection between 1992 and 2005. The median follow-up is 12.7 years. 71% was ER positive and 20% Her2 positive by IHC/FISH. 58% received adjuvant endocrine therapy (ET) (excluding 13 patients unknown treatment), 64% received adjuvant chemotherapy (CT) (excluding 12 patients unknown treatment) and 33% received both. Results: 61 (34%) Patients with MammaPrint Low Risk/Luminal-type (Luminal A) showed 5-year DFS of 97% (34% received CT and 69% ET) and 50 (28%) patients with MammaPrint High Risk/Luminal-type (Luminal B) had a 5-year DFS of 98% (60% received CT and 68% ET). Patients with BluePrint Basal-type tumors (46 (26%)) had a 5-year DFS of 80% (78% received CT); HER2-type (23 (13%)) had a 5-year DFS of 78% (87% received CT without HER2 targeted therapy). Conclusions: In this retrospective study evaluating 180 US patients with early BC treated according to standard guidelines we showed how combining BluePrint with MammaPrint can detect molecularly defined subgroups of patients who are at high risk of recurrence (HER2 and Basal-type). Furthermore, we confirmed that molecularly defined Luminal type disease is associated with excellent disease-free survival. MammaPrint and BluePrint molecular and prognostic stratification should be prospectively evaluated for therapeutic selection.