S5-1: Neoadjuvant Pertuzumab (P) and Trastuzumab (H): Biomarker Analyses of a 4-Arm Randomized Phase II Study (NeoSphere) in Patients (pts) with HER2−Positive Breast Cancer (BC).

Abstract

Background: NeoSphere showed that P with H and docetaxel (T) had a significantly higher pCR rate (45.8%) compared with TH (29%) or other P combinations (HP, TP) (Gianni, SABCS 2010). HER2+/ER+ and HER2+/ER− BC have different patterns of gene expression, and treatment response seems to be driven by different biologic pathways (Bianchini, ASCO 2011). This effect was also seen in NeoSphere. A broad panel of biomarkers (BMs) was assessed in tumor specimens and in sera to characterize the molecular profile of the ITT population and to explore BMs with different treatments and in different subsets of pts. Methods: Core biopsies and sera from 387/417 pts collected at baseline were available for BM analyses. HER2, all its truncated forms, HER3, IGF1R, PTEN, and pAKT were assessed by IHC and a modified H-score was derived per each marker. HER1, HER2, HER3, amphiregulin (AREG) and betacellulin mRNA expression in tumor tissue was assessed by qRT-PCR. C-myc was assessed by FISH. Mutational analyses of 8 hot spots within PIK3CA on tumor DNA was done via TaqMan-PCR. ELISA was used to detect HER2 extracellular domain (ECD), AREG, EGF, and TGFα in serum. Treatment interaction test was performed to test for association between BMs and pCR. In the analysis, median values were used as cutoffs, except for PTEN, PIK3CA mutation, and c-myc amplification, where cutoffs were applied following a biologic rationale. Results: In the overall population, high HER2 membrane protein expression measured by modified H-score was associated with a significantly higher pCR rate in the THP arm (p=0.001), with a large benefit from combination of P with TH (OR=3.74, CI 80%, 2.21−6.34; p=0.0009). The cutoff derived from NeoSphere has no immediate clinical applicability. A decreased likelihood of pCR was detected for pts with PI3K mutations in all 4 arms in a preliminary analysis limited to about 70% of cases. A final analysis will be presented. A significantly different distribution of BM expression in the ER+ vs ER− subgroups was found for 10 of 16 BMs (FDR<0.05). Low levels of IGF1R were found to be associated with higher pCR with combination of P with TH in the ER− (OR=4.40, CI 80%, 2.17−8.9; p=0.006) but not ER+ subgroup. High HER2 mRNA expression was associated with higher pCR rate in the HP arm in ER− (p=0.021) but not ER+ (p=0.74) tumors. Data on the full BM analysis including those on the ratio between HER2 ECD and intracellular domain (p95) will be presented. The levels measured for AREG and betacellulin were generally very low (less than the limits of variability for these assays), hence further analysis was not felt meaningful. Summary: The level of HER2 membrane protein expression was associated with increased benefit from combination of P with TH. The PI3K mutational status appears to have a relevant role in defining the likelihood of response with all treatments. The different treatment effects according to ER status are reflected in a different molecular BM profile in ER+ vs ER− tumors, with the IGF1R membrane score being correlated with ER− tumors. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr S5-1.

Predictive Factors for Response to Neoadjuvant Therapy in Breast Cancer

“…The lowest pCR rate of only 6.3% was found within an HER2+/HR+ cohort harbouring a PIK3CA mutation, identifying HR status in addition to PIK3CA mutation as an independent predictor of pCR in HER2+ BC. Those results are in concordance with data from the Neo-ALTTO [59], Neosphere [60] and the TBCRC 006 [61] studies, and the concept has paved the way for the development of new treatment options with PI3K -targeting agents. In the phase II Neophoebe study (NCT01816594), HER2-+ patients are stratified according to their PIK3CA mutation status and randomized within each cohort to neoadjuvant trastuzumab versus trastuzumab + BKM120 (a potent and highly specific oral pan-class I PI3K inhibitor) in combination with weekly paclitaxel.…”

Quantitative Measurements of Tumoral p95HER2 Protein Expression in Metastatic Breast Cancer Patients Treated with Trastuzumab: Independent Validation of the p95HER2 Clinical Cutoff

“…Not surprisingly, attempts to infer active p95 levels by comparing HER2 intracellular and extracellular domain content have led to inconsistent results (13). Even if the expression of various HER2-CTFs were correlated to some degree, obtaining an accurate measure of the minor component of active HER2-CTF would be plagued by a high degree of variability.…”

18F-FDG PET/CT for Early Prediction of Response to Neoadjuvant Lapatinib, Trastuzumab, and Their Combination in HER2-Positive Breast Cancer: Results from Neo-ALTTO

“…More recent research into anti-HER2 therapies indicates that using 2 anti-HER2 agents to create a dual blockade offers further significant clinical advantages (22,23), but here also biomarker research has been unsuccessful (24).…”