[Prognostic and predictive impact of protein expression profiling in high risk breast cancer patients treated with...

The prognostic and predictive impact of protein expression profiles was analyzed in high-risk breast cancer patients who had previously been shown to benefit from high-dose chemotherapy (HDCT) in comparison to dose-dense chemotherapy (DDCT). Using tissue microarrays, the expression of 34 protein markers was evaluated in 236 patients who had received either HDCT or DDCT (in the WSG AM01 trial). 1) 24 protein markers of the initial panel of 34 markers were sufficient to identify five profile clusters by K-means clustering: luminal A (27%), luminal B (12%), HER-2 (21%), basal-like (13%) cluster and a so called 'multiple marker negative'=MMN cluster (27%) characterized by the absence of specifying markers. 2) After DDCT, HER-2 and basal-like groups had significantly worse event-free survival (EFS) (HR 3.6 (95% CI, 1.65-8.18; p = 0.001) and HR 3.7 (95% CI, 1.68-8.48); p < 0.0001), respectively) when compared to both luminal groups. 3) After HDCT, the hazard ratio was 1.5 (95% CI, 0.76-3.05) for EFS in the HER-2 subgroups and 1.1 (95% CI, 0.37-3.32) in the basal-like subgroups which indicates a better outcome for patients in the HER-2 and basal-like subgroups who received HDCT. Protein expression profiling in high-risk breast cancers identified 5 subtypes, which differed with respect to survival and response to chemotherapy: In contrast to luminal A and B subtypes, HER-2 and basal-like subgroups had a significant predictive benefit from HDCT when compared to DDCT.