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Background: The lapatinib-taxane combination led to shorter PFS than trastuzumab-taxane in HER2+ metastatic breast cancer. We investigated the prognostic and predictive effects of pretreatment serum HER2, CAIX, and TIMP-1., Methods: MA.31 accrued 652 patients; 537 (82%) were centrally confirmed HER2+. Biomarkers were categorized for univariate and multivariable predictive investigations with a median cut-point, ULN cut-points (15 ng/ml for HER2; 506 pg/ml for CAIX; 454 pg/ml for TIMP-1), and custom cut-points (30 and 100 ng/ml for HER2). Stratified step-wise forward Cox multivariable analysis examined continuous and categorical effects of biomarkers on PFS in the ITT and central HER2+ populations; central HER2+ biomarker results are shown., Results: Serum was banked for 472 (72%) of 652 patients. Higher serum HER2 (>median; >15; >30; or >100 ng/ml; p = 0.05-0.002); higher CAIX (>median; >506 pg/ml; p = 0.02; p = 0.001); and higher TIMP-1 (> median; > 454 pg/ml; p = 0.001; p = 0.02) had shorter univariate PFS. In multivariable analysis, higher continuous TIMP-1 was associated with significantly shorter PFS: HR = 1.001 (95% CI = 1.00-01.002; p = 0.004). Continuous serum HER2 and CAIX were not significantly associated with PFS. HER2 of 15 ng/ml or higher had shorter PFS (p = 0.02); higher categorical CAIX had shorter PFS (p = 0.01-0.08). Interaction terms of HER2, CAIX, and TIMP-1 with treatment were not significant; the predictive test power was low., Conclusions: Higher levels of serum TIMP-1, CAIX, and HER2 were significant prognostic biomarkers of shorter PFS. We found no significant interaction between serum biomarkers and response to lapatinib versus trastuzumab. Evaluation of TIMP-1 and CAIX-targeted therapy in addition to HER2-targeted therapy appears warranted in patients with elevated serum levels of these biomarkers.

Trastuzumab is effective in the treatment of HER2/neu over-expressing breast cancer, but not all patients benefit from it. In vitro data suggest a role for HER3 in the initiation of signaling activity involving the AKT–mTOR pathway leading to trastuzumab insensitivity. We sought to investigate the potential of HER3 alone and in the context of p95HER2 (p95), a trastuzumab resistance marker, as biomarkers of trastuzumab escape. Using the VeraTag® assay platform, we developed a dual antibody proximity-based assay for the precise quantitation of HER3 total protein (H3T) from formalin-fixed paraffin-embedded (FFPE) breast tumors. We then measured H3T in 89 patients with metastatic breast cancer treated with trastuzumab-based therapy, and correlated the results with progression-free survival and overall survival using Kaplan–Meier and decision tree analyses that also included HER2 total (H2T) and p95 expression levels. Within the sub-population of patients that over-expressed HER2, high levels of HER3 and/or p95 protein expression were significantly associated with poor clinical outcomes on trastuzumab-based therapy. Based on quantitative H3T, p95, and H2T measurements, multiple subtypes of HER2-positive breast cancer were identified that differ in their outcome following trastuzumab therapy. These data suggest that HER3 and p95 are informative biomarkers of clinical outcomes on trastuzumab therapy, and that multiple subtypes of HER2-positive breast cancer may be defined by quantitative measurements of H3T, p95, and H2T.

Background Endoglin (CD105) is a co-receptor for TGF-beta, is expressed by human vascular endothelial cells, and plays a major role in angiogenesis. Materials and methods Pretreatment EDTA plasma from 224 metastatic breast cancer patients enrolled in a phase III 2nd-line hormone therapy trial and 50 control subjects were assayed for endoglin using an ELISA. Results The female control group (n = 50) plasma endoglin upper limit of normal was defined as the mean + 2 SD (8.7 ng/ml). The breast cancer patient plasma endoglin was 6.40 +/- 2.23 ng/ml (range 3.00-19.79 ng/ml). Elevated plasma endoglin levels were detected in 26 of 224 patients (11.6%). Patients with elevated plasma endoglin had a reduced clinical benefit rate (CR + PR + Stable) (15 vs. 42%) (P = 0.01) to hormone therapy. TTP was shorter for patients with elevated plasma endoglin, but did not reach statistical significance (P = 0.2). Patients with elevated plasma endoglin had decreased overall survival (median 645 vs. 947 days) (P = 0.005). Conclusion Elevated pretreatment plasma endoglin levels predicted for decreased clinical benefit and a shorter overall survival in metastatic breast cancer patients treated with 2nd-line hormone therapy.