High circulating HER2 extracellular domain levels correlate with reduced efficacy of an aromatase inhibitor in hormone receptor-positive metastatic breast cancer: A confirmatory prospective study

Prognostic Value of the Serum HER2 Extracellular Domain Level in Breast Cancer: A Systematic Review and Meta-Analysis

An elevated serum HER2 extracellular domain is associated with poor prognosis in breast cancer, but the relationship between sHER2 and the efficacy of different modalities remains controversial. Herein, we aimed to evaluate the prognostic value of serum HER2 extracellular domain (sHER2 ECD) in breast cancer and to identify its correlation with the efficacy of different treatment regimens. A systematic search of the PubMed, Embase, Cochrane Library, Web of Science, and Scopus databases was conducted to identify studies exploring the association between HER2 ECD level and clinical outcomes among patients with breast cancer. Using the random effects models, pooled hazard ratios (HRs), and odds ratios (ORs) with 95% confidence intervals (CI), were calculated for progression-free survival (PFS), overall survival (OS), disease-free survival (DFS), and the objective response rate (ORR). Heterogeneity was further evaluated by subgroup and sensitivity analysis. Overall, 40 studies comprising 12,229 patients were included in this systematic review and meta-analysis. Elevated HER2 ECD levels were associated with worse PFS (HR 1.74, 95% CI 1.40−2.17; p < 0.001), and this effect was observed in patients treated with chemotherapy (HR 1.81, 95% CI 1.37−2.39; p < 0.001), endocrine therapy (HR 1.91, 95% CI 1.57−2.32; p < 0.001), and trastuzumab (HR 1.74, 95% CI 1.31−2.30; p < 0.001). However, this association was not present in patients treated with tyrosine kinase inhibitors (TKIs) (HR 1.44, 95% CI 0.85−2.43, p = 0.17). The HRs/ORs for an elevated HER2 ECD level for DFS, OS, and ORR were 2.73 (95% CI 2.17−3.42; p < 0.001), 2.13 (95% CI 1.77−2.57; p < 0.001), and 0.80 (95% CI 0.49−1.31; p = 0.381), respectively. An elevated sHER2 ECD was an unfavorable prognostic factor in breast cancer but did not affect the efficacy of tyrosine kinase inhibitors such as lapatinib. Detection of sHER2 ECD may be helpful for clinicians selecting the appropriate anti-HER2 therapy for patients with HER2-positive breast cancer.

Clinical usefulness of human epidermal growth factor receptor-2 extracellular domain as a biomarker for monitoring cancer status and predicting the therapeutic efficacy in breast cancer

We assessed the clinical usefulness of human epidermal growth factor receptor-2 extracellular domain (HER2ECD) as a biomarker for detecting cancer and monitoring disease status and for predicting the efficacy of anticancer treatment in breast cancer. Five-hundred and eighty serum samples from 252 patients with breast cancer were examined for the concentration of HER2ECD to compare with conventional tumor markers (CEA, CA15-3, NCC-ST439 and BCA225). Also, in 19 patients with HER2-overexpressed advanced or recurrent breast cancer who were treated with trastuzumab, clinical outcomes were evaluated retrospectively to determine whether their serum HER2ECD levels predict clinical responses. The proportion of patients with elevated HER2ECD levels was 15.1%, which was compatible with those with elevated conventional marker levels. In patients with HER2-overexpressed breast cancer, the positive rate of HER2ECD was significantly higher (24.1%) than those of conventional markers (7.4-12.9%), suggesting the usefulness of HER2ECD for detecting cancer in this population. HER2-overexpressed patients responding to trastuzumab (12 of 19 patients) showed significantly higher serum HER2ECD level (p = 0.033) and longer time to progression (TTP) (p = 0.039) and overall survival (OS) (p = 0.031) than did patients not responding (seven patients). Furthermore, higher response rates were observed in patients with elevated HER2ECD levels than in patients without elevated HER2ECD levels (91.3% vs. 14.3%, p = 0.032), whereas there was no difference in survival between the two groups. The results suggest that HER2ECD is a useful biomarker not only for detecting breast cancer recurrence but also for predicting tumor responses to trastuzumab.

Serum HER2 testing in patients with HER2-positive breast cancer: the death knell tolls

Determination of the human epidermal growth factor receptor 2 (HER2; also known as ERBB2) status of breast tumours is emphasised in various national guidelines as a necessary step for the diagnosis of breast cancer. As an alternative to tissue-based diagnostic methods, there has been substantial interest in the establishment of an easily accessible serum-based alternative that could be used for prognosis and diagnosis. Detection of serum-soluble-HER2 extracellular domain (ECD) and establishment of its potential clinical usefulness has created much debate. We assessed whether identification of circulating concentrations of HER2 ECD have clinical usefulness for management of patients with HER2-positive breast cancer. We examined data from 63 studies of patients with breast cancer. Prevalence of increased concentrations varied greatly between studies. Some studies showed significant associations between raised concentrations and poor prognosis, poor response to treatments including trastuzumab, or tumour characteristics associated with aggressive disease, whereas others did not. Examination of existing data showed that concentrations of HER2 ECD are not consistently related to patient outcomes; therefore, there is insufficient evidence to support the clinical use of serum HER2 ECD testing. Design and execution of future large-scale trials to investigate the clinical use of HER2 ECD testing, in view of the progressive non-supportive evidence, is not recommended. Oncologists should continue to adhere to national guidelines for determining HER2 status. Furthermore, oncologists should continue to use clinical parameters when making decisions about initiation, continuation, and discontinuation of HER2-targeted treatments.

Prognostic and predictive value of HER2 extracellular domain in metastatic breast cancer treated with lapatinib and paclitaxel in a randomized phase III study

PURPOSE

The HER2 extracellular domain (ECD) is enzymatically cleaved from the cell membrane. Shed ECD in serum has been studied as both prognostic and predictive markers. Lapatinib is a dual inhibitor of HER2 and epidermal growth factor receptor kinases. We examined the prognostic and predictive role of HER2 ECD in a randomized trial of paclitaxel with placebo or lapatinib in women with HER2-negative or -unknown breast cancer.

PATIENTS AND METHODS

Patients (n = 579) with newly diagnosed metastatic breast cancer (MBC) were randomly assigned to paclitaxel with placebo or lapatinib. HER2 status was determined centrally. ECD was centrally measured by enzyme linked immunoassay in available samples at baseline (b; n = 472), week 9, and every 12 weeks thereafter. Results were correlated to overall response rate (ORR) and progression-free survival (PFS).

RESULTS

Elevated baseline ECD (bECD) levels (>or= 16 ng/mL) did not predict HER2 tumor status (sensitivity, 62%; specificity, 75%). In HER2-negative tumors, elevated bECD was not correlated with improved efficacy for lapatinib plus paclitaxel versus placebo plus paclitaxel (ORR: odds ratio, 1.6; 95% CI, 0.1 to 3.8; P = .365; PFS: hazard ratio, 0.94; 95% CI, 0.60 to 1.47; P = .797). ECD levels tended to decrease over time when bECD was elevated. ECD conversion from low to high was associated with worse PFS. Converting from high to low was associated with a better PFS. A consistently low ECD level had better PFS than a consistently elevated ECD. All associations were found to be independent of lapatinib.

CONCLUSION

HER2 bECD does not predict lapatinib benefit in patients with HER2-negative MBC. Changes in ECD status correlates with patient outcome regardless of treatment given. Measuring HER2 ECD is not currently recommended for predicting benefit to lapatinib.