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Keywords:

  • breast cancer;
  • human epidermal growth factor receptor 2;
  • HER2-positive;
  • serum HER2;
  • extracellular domain;
  • biomarker

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SUPPORT
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES

BACKGROUND

Increased soluble human epidermal growth factor receptor 2 (sHER2) is an indicator of a poor prognosis in HER2-positive metastatic breast cancer. In this study, the authors evaluated levels of sHER2 during treatment and at the time of disease recurrence in the adjuvant North Central Cancer Treatment Group N9831 clinical trial.

METHODS

The objectives were to describe sHER2 levels during treatment and at the time of recurrence in patients who were randomized to treatment arms A (standard chemotherapy), B (standard chemotherapy with sequential trastuzumab), and C (standard chemotherapy with concurrent trastuzumab). Baseline samples were available from 2318 patients, serial samples were available from 105 patients, and recurrence samples were available from 124 patients. The cutoff sHER2 value for the assay was 15 ng/mL. Statistical methods included repeated measures linear models, Wilcoxon rank-sum tests, and Cox regression models.

RESULTS

There were differences between groups in terms of age, menopausal status, and hormone receptor status. Within treatment arms A, B, and C, patients who had baseline sHER2 levels ≥15 ng/mL had worse disease-free survival than patients who had baseline sHER2 levels <15 ng/mL (arm A: hazard ratio, 1.81; P = .0014; arm B: hazard ratio, 2.08; P = .0015; arm C: hazard ratio, 1.96; P = .01). Among the 124 patients who experienced disease recurrence, sHER2 levels increased from baseline to the time of recurrence in arms A and B but remained unchanged in arm C. Patients who had recurrence sHER2 levels ≥15 ng/mL had a shorter survival after recurrence with a 3-year overall survival rate of 51% compared with 77% for those who had recurrence sHER2 levels <15 ng/mL (hazard ratio, 2.36; 95% confidence interval, 1.19-4.70; P = .01).

CONCLUSIONS

In patients with early stage, HER2-positive breast cancer, a high baseline sHER2 level was identified as a prognostic marker associated with shorter disease-free survival, and a high sHER2 level at recurrence was predictive of shorter survival. Cancer 2013;119:2675–2682. © 2013 American Cancer Society.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SUPPORT
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES

Breast cancer is a significant health problem worldwide, with an estimated 1.38 million women diagnosed annually.[1] There remains a significant interest in and a need to identify prognostic and predictive characteristics of the disease to help understand its natural history and its impact on therapeutic selection.[2] The discovery of amplification and/or overexpression of the tyrosine kinase human epidermal growth factor receptor 2 (HER2) in 15% to 20% of invasive breast cancers and the correlation of HER2 overexpression with a worse prognosis in both locoregional and advanced disease have revolutionized the understanding of the prognosis and therapeutic management of patients with breast cancer.[3]

Clinical advancements have principally been accomplished with the use of trastuzumab, a fully humanized monoclonal antibody against HER2 that has demonstrated activity against HER2-overexpressing, invasive breast cancers in both locoregional and advanced disease.[4-7] Identifying biologic predictors to optimize prognosis and selecting patients for anti-HER2 therapy with or without other therapies are significant foci of our research and that of others.

In addition to evaluating HER2 and other molecular markers in tissue specimens, there has been great interest in serologic-based testing for circulating HER2 because of the accessibility of serologic testing and the possibility of serial monitoring for tumor response to therapy.[8] HER2 is a 185-kDa protein composed of an intracellular domain, a transmembrane, and an extracellular domain (ECD). The ECD is occasionally cleaved by matrix metalloproteinases and is released into the peripheral circulation as soluble HER2 (sHER2),[9] where it can be quantified using commercially available enzyme-linked immunosorbent assays.[10] Therefore, sHER2 is a logical marker to evaluate as a prognostic and/or predictive factor in the setting of metastatic and early stage HER2-overexpressing breast cancer.

Some data gathered over the last few years support the evaluation of this marker, whereas others do not.[11-14] Carney et al conducted a meta-analysis of 55 publications (>6500 patients) evaluating the prevalence, prognosis, prediction of response to therapy, and potential use of sHER2 for monitoring breast cancer.[11] In that study, from 0% to 38% of patients (mean, 18.5%) with HER2-positive, early stage breast cancer and from 23% to 80% of patients (mean, 43%) with metastatic breast cancer had sHER2 concentrations that were above the control cutoff described in each publication. Results from the meta-analysis suggested that a high circulating sHER2 level is a prognostic factor of inferior progression-free survival (PFS) and overall survival (OS) and a predictive factor of a poor response to endocrine therapy and some chemotherapy regimens. Those authors also noted that serial increases in sHER2 may precede the appearance of metastases and that longitudinal sHER2 changes could predict the clinical course of the underlying disease. Although the data regarding metastatic breast cancer demonstrate a possible correlation of tumor burden and clinical outcome with sHER2, there are very little data regarding the significance of sHER2 levels in the adjuvant setting. Our North Central Cancer Treatment Group adjuvant trial N9831 is an ideal study in which to explore the role of sHER2 as a potential prognostic or predictive marker, because it is a large prospective study of chemotherapy alone or with trastuzumab for patients with HER2-positive resected breast cancer.[15]

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SUPPORT
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES

The eligibility criteria and study design for N9831 have been previously reported.[4] Patients were required to have histologically confirmed adenocarcinoma of the breast with 3+ immunohistochemical staining for HER2 or amplification of the HER2 gene by fluorescence in situ hybridization (≥2.0 ratio) and with either lymph node-positive or high-risk lymph node-negative disease to be eligible for the study. The N9831 trial had 3 treatments arms (arm A: doxorubicin and cyclophosphamide every 3 weeks for 4 cycles followed by weekly paclitaxel for 12 weeks; arm B: sequential trastuzumab treatment with doxorubicin and cyclophosphamide every 3 weeks for 4 cycles, followed by weekly paclitaxel for 12 weeks, followed by 52 weeks of weekly trastuzumab; arm C: concurrent trastuzumab treatment, doxorubicin and cyclophosphamide every 3 weeks for 4 cycles, followed by weekly paclitaxel plus concurrent trastuzumab for 12 weeks, followed by 40 more weeks of weekly trastuzumab).

In a plan to examine correlations with clinical outcomes, serum samples were scheduled to be obtained at baseline from all patients (at study entry; all patients were postprimary surgical resection of tumors); throughout treatment in a subset of 35 patients per arm (every 3 months for the first year then every 6 months from year 2 to year 5; these samples were part of a planned cardiac marker substudy); and, when available, at the time of tumor recurrence for all patients who developed recurrent disease. The median follow-up for these patients was 4.7 years. Specimens were analyzed using the commercially available Advia Centaur serum HER2 assay (Wilex/Oncogene Science, Cambridge, Mass). Payne et al have demonstrated that trastuzumab does not interfere with this serum HER2 assay.[16]

The cutoff for this assay for normal and high sHER2 levels was 15 ng/mL according to the US Food and Drug Administration-approved ADVIA Centaur HER-2/neu assay recommendation. Of the total 3505 patients enrolled in the trial, baseline samples were available for 2318 patients participating in treatment arms A (n = 795), B (n = 814), and C (n = 709). For various reasons, 1187 patients were excluded from the statistical analysis, as outlined in Figure 1. Serial samples were available from 105 patients, and recurrence samples were available from 124 patients for analyses. Statistical methods included Wilcoxon rank-sum tests and Cox regression models. A linear mixed effects model was used in the analysis of serial sHER2 levels. DFS and OS analyses were stratified by estrogen receptor and progesterone receptor (ER/PR) status and by lymph node status. Multivariate analyses stratified by ER/PR and lymph node status were conducted including additional patient characteristics that were significant or borderline significant predictors of baseline sHER2 levels ≥15 ng/mL. These included menopausal status, age, tumor size, tumor grade, and race. Age was not included simultaneously with menopausal status in models because of their high correlation.

image

Figure 1. An analysis of soluble human epidermal growth factor receptor 2 (sHER2) levels from North Central Cancer Treatment Group (NCCTG) adjuvant trial N9831 is shown.

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RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SUPPORT
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES

Baseline characteristics between patients with sHER2 levels <15 ng/mL (n = 2029) and patients with sHER2 levels ≥15 ng/mL (n = 289) are listed in Table 1. Differences between groups existed by age, menopausal status (higher sHER2 levels in patients aged ≥50 years and in postmenopausal patients), and hormone receptor status (lower sHER2 levels in hormone receptor-positive tumors). Table 1 compares the characteristics of patients with and without baseline blood samples to assess sHER2 levels. Caucasians and patients with tumors <2 cm were more likely to have a blood sample available.

Table 1. Patient Characteristics According to Soluble HER2 Group at Baseline
   No. (%)  
CharacteristicsHER2 <15 ng/mL: No. (%)Chi-Square PsHER2 ≥15 ng/mLCohort PatientsChi-Square PNoncohort Patients: No. (%)
  1. Abbreviations: ER, estrogen receptor; PR, progesterone receptor; SBR, Scarff-Bloom-Richardson grading system; sHER2, soluble human epidermal growth factor receptor 2.

  2. a

    This P value was determined using the Mantel-Haenszel test for trend.

  3. b

    Patients who had missing data were not included in this comparison.

Total no. of patients2029 (88) 289 (12)2318 (74) 815 (26)
Age: Median [range], y49 [19-82] 53 [23-80]49 [19-82] 50 [22-79]
Age group, y      
<40373 (18)<.0001a26 (9)399 (17).15a145 (18)
40-49691 (34) 85 (29)776 (33) 261 (32)
50-59669 (33) 113 (39)782 (34) 238 (29)
≥60296 (15) 65 (22)361 (16) 171 (21)
Race      
White1723 (85).08234 (81)1957 (84).05664 (81)
Other306 (15) 55 (19)361 (16) 151 (19)
Menopausal status      
Premenopausal or age <50 y1147 (57)< .0001107 (37)1254 (54).59432 (53)
Postmenopausal or age ≥50 y882 (43) 182 (63)1064 (46) 383 (47)
ER/PR status      
ER or PR positive1112 (55).01135 (47)1247 (54).78443 (54)
Other917 (45) 154 (53)1071 (46) 372 (46)
Surgery      
Breast conserving796 (39).77116 (40)912 (39).18299 (37)
Mastectomy1233 (61) 173 (60)1406 (61) 516 (63)
Lymph node status      
Positive1751 (86).09260 (90)2011 (87).93706 (87)
Negative278 (14) 29 (10)307 (13) 109 (13)
Predominant histology      
Ductal1922 (95).98b274 (95)2196 (95).51b767 (94)
Lobular59 (3) 8 (3)67 (3) 30 (4)
Other46 (2) 7 (2)53 (2) 17 (2)
Missing2 (0.1) 0 (0)2 (0.1) 1 (0.2)
Histologic tumor grade: Elston/SBR      
Well/moderately differentiated589 (29).1271 (25)660 (28).84235 (29)
Poorly differentiated1440 (71) 218 (75)1658 (72) 580 (71)
Pathologic tumor size, cm      
<2705 (35).0785 (29)790 (34).02242 (30)
≥21324 (65) 204 (71)1528 (66) 573 (70)
Hormone treatment      
Yes1088 (54).0002122 (42)1210 (52).77b418 (51)
No930 (46) 166 (57)1096 (47) 388 (48)
Missing11 (0.5) 1 (0.3)12 (0.5) 9 (1)

Within treatment arms A, B and C, patients who had baseline sHER2 levels ≥15 ng/mL had worse DFS than patients who had baseline sHER2 levels <15 ng/mL (arm A: hazard ratio [HR], 1.81; P = .0014; arm B: HR, 2.08; P = .0015; arm C: HR, 1.96; P = .01) (Table 2). Table 3 displays a DFS multivariate analysis across all 3 treatment arms. sHER2 levels ≥15 ng/mL remained unchanged (HR, 1.95 in both analyses). Similarly, multivariate analyses were performed within each treatment arm and had minimal effect on sHER2 HRs. With regard to hormone receptor status, the association of sHER2 with DFS was present within the ER/PR-positive and ER/PR-negative subgroups (Table 3).

Table 2. Disease-Free Survival by Treatment Arm and Baseline Soluble Human Epidermal Growth Factor Receptor 2 Level, N = 2318
      DFS, %
sHER2 Group, ng/mLNo. of PatientsNo. of EventsHRa95% CIP3-Year5-Year
  1. Abbreviations: CI, confidence interval; HR, hazard ratio; sHER2, soluble human epidermal growth factor receptor 2.

  2. a

    This analysis was stratified by hormone receptor status and lymph node status.

All treatment arms       
<1520292771.00 < .000187.381.9
≥15289861.951.52-2.49 71.563.7
Arm A       
<156841171.00 .001483.676.5
≥15111411.811.26-2.61 64.756.1
Arm B       
<15723911.00 .001588.183.4
≥1591252.081.32-3.27 76.667.7
Arm C       
<15622691.00 .0190.786.3
≥1587201.961.16-3.33 75.370
All treatment arms       
<10.0678841.00  86.782.2
10.0-11.5536700.910.66-1.25.5788.884.1
11.5-13.5583861.030.76-1.40.8386.680.4
≥13.5521 1.571.19-2.08.00278.270.6
Table 3. Disease-Free Survival: Multivariate Analysis Across All 3 Three Treatment Arms
Covariate: All Treatment ArmsHRa95% CIP
  1. Abbreviations: CI, confidence interval; HR, hazard ratio; sHER2, soluble human epidermal growth factor receptor 2.

  2. a

    This analysis was stratified by hormone receptor status and lymph node status.

sHER2 ≥151.951.52-2.50< .0001
Race0.970.72-1.29.81
Menopausal status0.940.76-1.16.56
Histologic tumor grade1.010.80-1.29.92
Tumor size ≥2 cm1.200.95-1.50.13

Analyzing serial sHER2 levels during treatment, the mean loge sHER2 level remained constant over time in arm C (estimated slope, 0.003; P = .43), whereas the estimated increase per month was 0.010 (loge scale) for arm B (P = .07) and 0.022 (loge scale) for arm A (P ≤ .0001). On the basis of the linear mixed model at 18 months, the mean loge sHER2 was 2.98 (95% confidence interval [CI], 2.88-3.08) for arm A, 2.72 (95% CI, 2.62-2.82) for arm B, and 2.55 (95% CI, 2.42-2.68) for arm C.

Among the 124 patients who developed disease recurrence and had serum samples available for this test, sHER2 levels increased from baseline to the time of recurrence in arm A (mean, 73.4 ng/mL; median, 1.8 ng/mL; P = .005) (Fig. 2, top) and in arm B (mean, 48.2 ng/mL; median, 2.2 ng/mL; P = .01) (Fig. 2, middle), but sHER2 levels remained unchanged in arm C (mean, 9.1 ng/mL; median, −0.3 ng/mL; P = .66) (Fig. 2, bottom). Patients who had recurrence sHER2 levels ≥15 ng/mL had a shorter survival after recurrence, with a 3-year OS rate of 51% compared with 77% for the <15 ng/mL sHER2 group (HR, 2.36; 95% CI, 1.19-4.70; P = .01).

image

Figure 2. Changes in soluble human epidermal growth factor receptor 2 (sHER2) levels from baseline to recurrence (scale, from 0 to 650 ng/mL) are illustrated for (Top) treatment arm A, (Middle) treatment arm B, and (Bottom) treatment arm C.

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DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SUPPORT
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES

Some small studies and subsequent meta-analyses that were published before the widespread use of HER2-directed therapies demonstrated a correlation between elevated baseline sHER2 levels and shorter survival in patients with metastatic breast cancer.[11, 17] Although the clinical importance of sHER2 has been studied extensively in metastatic breast cancer, to date, no consensus has been reached, and there are little available data regarding the use of sHER2 in locoregional breast cancer or in the era of multiple anti-HER2 therapies. A prospective study of 256 consecutive patients with stage I through III breast cancer demonstrated that sHER2 levels were high in 9% of patients, and the concordance of high sHER2 levels with positive HER2 status in tumor tissue was 87.1%.[18] High sHER2 levels were strongly associated with higher disease stage, higher histologic grade, and negative ER/PR status. Multivariate analysis identified high sHER2 levels as an independent prognostic factor of wore DFS. Recently, data have been published regarding the potential role of sHER2 in the neoadjuvant setting. In the GeparQuattro study, investigators assessed whether evaluation of a serum marker like sHER2 could help monitor and optimize treatment in 175 patients with early stage breast cancer who participated in that large neoadjuvant clinical trial.[19] The sHER2 level was measured before treatment initiation and after neoadjuvant chemotherapy (presurgery) in HER2-positive (n = 90) and HER2 negative (n = 85) patient cohorts. That study demonstrated a significant, positive association between high baseline sHER2 values and achieving a pathologic complete response (pCR) at the time of surgery in patients with HER2-positive tumors. A similar correlation also was observed with a decrease in sHER2 levels during neoadjuvant chemotherapy. However, as expected, no such association between sHER2 levels and pCR was observed in the subset of patients who had HER2 negative disease. In a follow-up neoadjuvant study, GeparQuinto, the same investigators noted that higher prechemotherapy sHER2 levels (>15 ng/mL) also were associated with higher pCR rates.[20] However, sHER2 levels changed differently during neoadjuvant therapy, with higher declines noted in patients who received trastuzumab than in those who received lapatinib. If a pCR is the best surrogate of improved long-term outcome, then a higher baseline sHER2 level would seem to indicate lower recurrence rates down the road for these patients who received with neoadjuvant therapy. This may initially seem contradictory to our finding, but the situation of these patients is different. A high baseline sHER2 level in the GeparQuattro and GeparQuinto studies may only reflect higher tumor burden, and its decline with neoadjuvant therapy and subsequent achievement of a pCR may reflect a population of patients with treatment-sensitive disease. However, ours was a study population of patients whose primary tumors had been resected several weeks earlier; thus, a higher baseline sHER2 level may represent a population of patients with residual circulating malignant cells that inherently have a higher residual risk of systemic relapse.

Data from the adjuvant, early stage, HER2-positive breast cancer N9831 translational clinical trial present a unique opportunity for the examination of meaningful associations and trends between clinical outcome and biomarkers of disease. In the N9831 study, 12% of the 2318 women who enrolled in the study after undergoing breast cancer resection and who had serum available and approved for use by written consent, had baseline elevation of sHER2 (289 of 2318 patients). This is consistent with the percentages reported previously in the meta-analysis of greater than 6500 patients reported by Carney et al[11] and in the study by Ludovini et al.[18]

In the N9831 trial, higher sHER2 levels were noted in patients aged ≥50 years, in postmenopausal patients, and in those with negative hormone receptor status. Whether there is a biologic reason for this correlation is unclear. Patients with high baseline sHER2 levels demonstrated significantly worse DFS in arm A (standard chemotherapy without trastuzumab) compared with patients who had normal levels, confirming the prognostic relevance of this marker in patients with HER2-positive breast cancer who do not receive trastuzumab. There also was a correlation of elevated baseline sHER2 with worse DFS in patients on arm C (standard chemotherapy plus concurrent trastuzumab) who had elevated baseline sHER2 levels (HR, 1.96; P = .01). Again, this is in keeping with some of the data published in the metastatic setting, suggesting that patients with elevated sHER2 levels at baseline have inferior outcomes, in this case, even when they received treatment with trastuzumab.[11, 17]

It is important to note the differences in trends in sHER2 levels between arm A (without trastuzumab) and arm C (with trastuzumab). sHER2 levels progressively increased in patients who developed tumor recurrence but did not receive HER2-directed therapy, whereas levels remained fairly stable in patients who received concurrent chemotherapy and trastuzumab. This trend persisted in patients who developed disease recurrence in both treatment arms. Although this observation is intriguing, the reasons for these data are unclear, and we hope that this issue will be readdressed in other data sets (and/or by other investigators). In the meantime, we can speculate that there may be biologic reasons for these observations, such as the possibility that trastuzumab therapy may directly inhibit the detection of sHER2. Molina et al demonstrated that trastuzumab prevents sHER2 shedding by inhibition of basal and activated HER2 proteolytic cleavage well before it induces any detectable decrease in cell surface HER2.[21] It is also possible that relapse in patients who did not receive trastuzumab therapy is primarily mediated by the classic HER2 pathway, although patients on the trastuzumab-containing arm who experienced progression developed it independent of the HER2 oncoprotein or through alternative pathways that confer acquired resistance to trastuzumab.

On the basis of the results presented herein, we can conclude that, in patients with early stage, resected, HER2-positive breast cancer, sHER is a prognostic marker associated with shorter DFS and that a high recurrence sHER2 level is predictive of shorter survival. This test may help enhance the prognostic information and, thus, assist in patient education and further studies (such as including patients with high sHER2 levels in studies to further evaluate novel therapeutic strategies that enhance the activity of chemotherapy with trastuzumab).

One of the main autocritiques of this study is that we started the correlative section with baseline samples from 2318 patients, but we were able to obtain completed serial samples from only 105 patients and recurrence samples from only 124 patients. Unfortunately, this is a recurring theme with large prospective trials, although our study has the largest matched sets between baseline and recurrent specimens in the adjuvant setting. Patients and participating institutions are initially eager to participate in these collections of samples for correlative sciences; however, as time goes on or as patients are confronted with updated consents to sign, the number of collections drops significantly. The small sample size at the time of recurrence makes it difficult to draw absolute conclusions about why sHER2 levels did not increase among patients in arm C (which is the current standard of care) compared with arm A.

Our study has been successful as a tool to explore the prognostic and predictive value of sHER in patients with early stage, HER2-positive breast cancer in 1 of the several early pivotal trials of adjuvant trastuzumab, but it in no way tries to be a comprehensive review of this test and of its role in the management of such patients. Several other biomarkers that have demonstrated promise in preclinical models are being evaluated in many of the already completed, large adjuvant HER2 clinical trials for their potential to prognosticate risk of disease recurrence and predict response to anti-HER2-based therapies. To date, none of those trials have reliably had clinical significance, including p95 HER2,[22, 23] PTEN,[24] PI3-kinase,[25, 26] topoisomerase IIα,[27-30] C-MYC,[31] and IGF-1R.[32, 33] Additional prospective studies are needed to further evaluate the role of sHER2 testing in the neoadjuvant, adjuvant, and metastatic settings, especially within the context of trials using newer HER2-directed therapies, such as lapatinib, pertuzumab, and trastuzumab-emtansine.

FUNDING SUPPORT

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SUPPORT
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES

This work was supported by National Institutes of Health grants CA25224 and CA114740, Genentech, Bayer, and the Breast Cancer Research Foundation.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. FUNDING SUPPORT
  8. CONFLICT OF INTEREST DISCLOSURES
  9. REFERENCES
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