Background: Classification into molecular subtypes may increasingly be important for the selection of therapy for patients with early-stage breast cancer. Previous analyses had shown that breast cancer subtypes have distinct clinical outcome [Sorlie et al. PNAS 2001; Esserman et al. BCRT 2011]. In our study, we analyzed the response to neo-adjuvant chemotherapy and long-term outcomes using the 70-gene profile (MammaPrint) together with an 80-gene molecular subtyping profile (BluePrint).

Methods: This analysis was performed on data from 421 patients: 141 patients from the I-SPY I trial; 230 patients from the biomarker discovery program at MD Anderson (131 and 99 respectively; Hess et al. JCO 2006; Iwamoto et al. BCRT 2011]; and 50 patients from the City of Hope [Somlo et al. ASCO 2010]. All patients were treated in the neo-adjuvant setting with chemotherapy. MammaPrint and BluePrint outcomes were determined from either 44K Agilent arrays run at Agendia or available through the I-SPY I data portal, or from Affymetrix U133A arrays. The combination of MammaPrint and BluePrint resulted in four 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 defined BluePrint molecular subgroups. pCR was observed in 3% of the Luminal A and 12% of Luminal B, in 38% of the HER2-type and in 42% of the Basal-type samples. 42% of patients with clinical HER2-positive phenotype are classified as Luminal-type by BluePrint: eight patients as Luminal A and 34 patients as Luminal B. 5-year distant metastases-free survival (DMFS) of patients with HER2-type by BluePrint who achieve pCR is 87%, compared with 78% for clinical HER2+ patients with pCR. These data are in line with a recent retrospective analysis of a large cohort of patients, which showed that pCR rate is not a suitable surrogate for clinical HER2+/Hormone Receptor-positive patients and is not associated with outcome [von Minckwitz et al. JCO 2012]. BluePrint classifies more patients as Basal-type (n = 120) with higher pCR rate (42%), compared with clinical subtyping (triple negative, n=93) with a pCR rate of 31%. Despite including eight clinical HER2+ and 11 triple-negative patients, those with BluePrint Luminal A subtype (n = 88) have excellent 5-year DMFS of 94% and appear to have no benefit from chemotherapy (low pCR rate).

Conclusions: Molecular subtyping using BluePrint with MammaPrint can help to improve outcomes of patients in the neo-adjuvant setting over clinical subtyping. We observed differences in pCR and DMFS following neo-adjuvant treatment in groups stratified by MammaPrint and BluePrint; for example, patients with Luminal A breast cancer (assessed with MammaPrint and BluePrint) have a good baseline prognosis with excellent survival and may not benefit from chemotherapy.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-06-11.