Abstract P2-05-21: Predictive value of quantitative HER2 and HER3 levels combined with downstream signaling markers in HER2-positive advanced breast cancer patients treated with lapatinib

Background: Clinical correlates of lapatinib resistance have not been well defined. Previous studies implicated genes regulated by the estrogen receptor (ER) and activation or mutation of proteins downstream from HER family receptors. In the current study, HER2 and HER3 expression levels were quantitatively measured using a VeraTag® fluorescence-based assay, in addition to seven downstream signaling proteins determined by IHC. All biomarkers were correlated with overall survival (OS) in patients treated with lapatinib.

Methods: Formalin-fixed, paraffin-embedded samples were obtained from the primary tumor of 191 patients treated with lapatinib plus capecitabine following progression on trastuzumab. The HERmark® Breast Cancer Assay (Monogram Biosciences, South San Francisco) was used to quantify HER2 protein expression levels. HER3 protein expression was quantified using the VeraTag® technology (Monogram Biosciences). Expression of ER, PTEN, Cyclin E, HIF-2alpha, p-p70S6K, p-AMPK and p-MAPK were determined by IHC (Duchnowska et al., Oncotarget 2016; 7:550). OS analyses of HER2 and HER3 were stratified by key clinical variables, including stage and presence of a brain metastasis prior to lapatinib-based therapy.

Results: Among the downstream signaling molecules, HIF-2alpha (r = -0.23; p = 0.047) and ER (r = -0.27; p = 0.005) were negatively correlated with HER2 expression after adjustment for multiple testing. PTEN appeared to correlate with HER3, but was not significant after adjustment for multiple testing. OS was significantly shorter for both those below the cut-off level of positivity by the HERmark assay (HR = 1.8; p = 0.029), and those with above median HER2 levels (HR = 1.7; p = 0.009), as compared to cases with in between levels. The relationship between HER2 and OS is also captured by a U-shaped, parabolic function in HER2 (p = 0.005). Elevated HER3 showed a trend toward a correlation with longer OS (HR = 0.66/log; p = 0.16), somewhat stronger in the ER-negative subset (HR = 0.55/log; p = 0.085) and in the subset with above-median HER2 (0.48/log; p = 0.10), where inhibiting HER2 activation of HER3 may be more important. In multivariate Cox models, HER2 (parabola, intermediate HER2 best, p = 0.001), presence of brain metastases (HR = 2; p < 0.001), ER (HR = 0.60; p = 0.009) and either p-p70S6K (HR = 0.66; p = 0.018) or p-AMPK (HR = 0.67; p = 0.022) were significantly associated with OS (p-p70S6K and p-AMPK were mutually correlated).

Conclusions: Patients with moderately increased HER2 levels may have best outcomes while receiving lapatinib following progression on trastuzumab. This supports recent findings of a less benefit from lapatinib in patients with high HER2 expression (Nunciforo et al., SABCS 2015, P3-07-08). HER3 levels do not seem to substantially impact the prognosis. Further studies are warranted to explore the predictive utility of quantitative HER2 and HER3 in guiding HER2-directed therapies.

Citation Format: Duchnowska R, Sperinde J, Czartoryska-Arlukowicz B, Mysliwiec P, Winslow J, Radecka B, Petropoulos C, Demlova R, Orlikowska M, Kowalczyk A, Lang I, Ziólkowska B, Debska-Szmich S, Merdalska M, Grela-Wojewoda A, Zawrocki A, Biernat W, Huang W, Jassem J. Predictive value of quantitative HER2 and HER3 levels combined with downstream signaling markers in HER2-positive advanced breast cancer patients treated with lapatinib [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-05-21.

Abstract P6-11-07: Quantitative p95HER2 levels in primary breast cancers and in matched brain metastases

Background: Patients with HER2-positive breast cancer are at high risk for brain metastases. A large number of HER2-positive tumors also express p95HER2 (p95), a truncated form of HER2 that lacks the trastuzumab binding site but retains kinase activity. Although p95 expression in primary breast tumors is well studied, the prevalence and significance of p95 expression in brain metastases is unknown. In the current study we examined expression of p95 in brain metastases and in matched primary breast tumors.

Methods: Seventy-five pairs of formalin-fixed paraffin-embedded samples from matched primary breast cancers and brain metastases were assayed for quantitative p95 protein expression using the p95 VeraTag® assay (Clin Cancer Res, 16:4226, 2010) specific for the M611 form of p95. Sufficient material to obtain p95 data in both primary and matched brain metastasis samples was available in 52 cases. In the remaining 23 cases, a p95 measurement was obtained in either the primary or brain metastasis sample. Estrogen (ER) and progesterone (PR) receptor status were scored using immunohistochemistry. Hormone receptor positivity was defined as either ER or PR positive. Quantitative HER2 protein expression was measured using the HERmark® assay. Both the p95 VeraTag assay and the HERmark assay measure tumor-averaged protein expression in units of relative fluorescence per mm2 tumor (RF/mm2). Measurements of p95 > 2.8 RF/mm2 and HER2 > 17.8 RF/mm2 were considered as positive results.

Results: There was a net increase in p95 expression in brain metastases relative to the matched primary tumor with a median increase of 1.5-fold (p = 0.001, range 0.2-fold to 35-fold). The increase in p95 expression was only weakly correlated with the increase in quantitative HER2 expression (R2 = 0.18; p = 0.0018). Cases with HERmark-positive tumors were more likely to have the largest (≥ 5-fold) increase in p95 expression compared to those with lower HER2 expression (odds ratio = 6.3; p = 0.018). Changes in p95 levels from primary to brain metastasis were unrelated to hormone receptor status (p = 0.59). P95 positivity in the primary tumor correlated with time from breast cancer diagnosis to first progression (HR = 2.2; p = 0.012) when stratified by hormone receptor status and tumor grade. Although there was a trend towards correlation of p95 positivity in the brain metastasis with time from diagnosis to brain metastasis (HR = 1.7; p = 0.058, stratified as above), p95 positivity did not correlate with overall survival from the time of brain metastasis diagnosis (HR = 1.3; p = 0.42, stratified as above).

Conclusions: This is the first study of quantitative p95 expression in matched primary tumors and brain metastases. Brain metastases of breast cancer show significant increases in p95 protein expression compared to matched primary tumors. These data provide a rationale for future correlative studies on p95 levels in brain metastases.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-11-07.

P2-12-05: Correlation between Quantitative HER2 Protein Expression and Risk of Brain Metastases in HER2−Positive Advanced Breast Cancer Patients Receiving Trastuzumab-Containing Therapy

Background. Patients with HER2−positive breast cancer are at particularly high risk for brain metastases; however, the biological basis is not fully understood. Within HER2−positive breast cancer tumors, it is possible to resolve a ∼1.5-log range of HER2 protein expression using a novel quantitative HER2 assay (HERmark®). We investigated the correlation between quantitative HER2 protein expression in primary breast cancers and the time to brain metastases (TTBM) in HER2−positive advanced breast cancer patients treated with trastuzumab.

Methods. The study group included 142 consecutive patients who were administered trastuzumab-based therapy for HER2−positive metastatic breast cancer, defined as 3+ categorical staining by immunohistochemistry (IHC). HER-2/neu gene copy number was subsequently quantified as HER2/CEP17 ratio by central laboratory fluorescence in situ hybridization (FISH). HER2 protein was quantified as total HER2 protein expression (H2T) by the HERmark assay in formalin-fixed, paraffin-embedded primary tumor samples. HER2 variables were correlated with clinical features and TTBM measured from the initiation of trastuzumab-containing therapy.

Results. H2T level (continuous variable) was correlated with shorter TTBM (HR=2.3; p=0.013), whereas HER2 gene amplification by FISH (p=0.28) and continuous HER2/CEP17 ratio (p=0.25) had no significant prognostic impact. The correlation between continuous H2T level and TTBM was confirmed in a multivariate analysis (HR=3.2; p=0.021). Controlling for the competing risk of death from causes other than brain metastases, continuous H2T remained a strong correlate of TTBM (HR=2.7; p=0.0009). In the subset of patients that was centrally-determined HER2 positive by FISH (117 patients), above-median H2T level was significantly associated with shorter TTBM (HR=2.4; p=0.005), whereas this was not true for median FISH/CEP17 ratio (p=0.4). In a multivariate analysis of this subset, continuous H2T (p=0.021) and a time dependent covariate capturing time to non-brain metastases (p=0.0044) were prognostic for TTBM, whereas FISH/CEP17, ER, PgR and grade were not.

Conclusions. These data reveal a strong relationship between quantitative HER2 protein expression levels and the risk of brain relapse in HER2−positive advanced breast cancer patients. Consequently, quantitative assessment of HER2 protein expression may inform and facilitate refinements in therapeutic treatment strategies for selected subpopulations of patients in this group.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-12-05.

P5-13-07: MET and Hepatocyte Growth Factor (HGF) Increased Gene Copy Number Is Associated to Trastuzumab Failure in HER2 Positive Metastatic Breast Cancer (MBC)

Background: The ErbB2-targeting monoclonal antibody trastuzumab has remarkable efficacy in metastatic breast cancer (MBC) patients (pts) with HER2 overexpression or amplification (HER2+), either alone or in combination with chemotherapy. However, the response rate to trastuzumab is modest and not all pts derive benefit from this treatment. Predictive mechanisms of sensitivity and/or resistance are largely unknown. Recently, preclinical and limited clinical data showed that aberrant MET expression in MBC is a predictor of poor prognosis and is involved in trastuzumab resistance. Aim of the present study was to investigate whether increased gene copy number of MET or its ligand, the hepatocyte growth factor (HGF), affect trastuzumab sensitivity.

Patients and Methods: This retrospective study included 130 HER2+ MBC pts treated with trastuzumab as monotherapy (N=21) or in combination with chemotherapy (N=109). Main inclusion criteria were presence of at least one measurable lesion and availability of paraffin-embedded tumor tissue from primary cancer. MET and HGF gene copy number (GCN) were assessed by fluorescence in situ hybridization (FISH). Receiver operating characteristic (ROC) analysis was used for identifying the best MET and HGF mean GCN cut-off.

Results: In the whole population response rate (RR), including complete (CR) and partial response (PR) was 49.2%, disease control rate, including CR+PR+ stable disease (SD) was 76.2%, median time to progression (TTP) 9.4 months, and median survival (OS) 28.3 months. MET FISH analysis was successfully performed in all 130 cases. Median MET mean GCN was 2.96 (range 1.66−8.40), with no gene amplification. ROC curve identified a mean of 3.72 MET GCN as the optimal cut-off value for discriminating between sensitive (CR+PR+SD) and refractory pts (pts with progressive disease [PD] at the first disease assessment). MET FISH+ (N=36, mean ≥3.72) had a significantly higher PD rate (44.4% versus 16.0%; p=0.001) and a significantly shorter TTP (5.7 versus 9.9 months; HR 1.74 95% C.I. 1.16−2.62; p=0.006) than MET FISH- pts (N=94, mean <3.72). HGF GCN was successfully evaluated in 84 pts (64.6%). Median HGF mean GCN was 2.80 (range 1.14−6.90). ROC analysis identified a cut-off of 3.01 mean HGF GCN as the best discriminating between sensitive (CR+PR+SD) and refractory pts. HGF FISH+ (N=33, mean ≥ 3.01) had a significantly higher PD rate (30.3% versus 7.8%; p=0.007) and a non-significant shorter TTP (9.9 versus 10.5 months, HR 1.10 95% C.I. 0.70−1.74, p=0.66).

Conclusions: High GCNs of MET or HGF associate with an increased risk of trastuzumab failure in HER2+ MBC. These data support a further development of combining anti-HER2 with anti-MET strategies in MBC.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-13-07.

Molecular characteristics of matched brain metastasis (BM) versus the primary breast cancer (PBC)

Abstract #2028

Background: Brain is increasingly a site of relapse in breast cancer patients, however the molecular patho-physiology of this process is not well understood. Using a novel assay allowing high-throughput analysis of gene expression from formalin-fixed paraffin-embedded (FFPET) tumor samples, we compared molecular characteristics of BM with those of the PBC in a series of breast cancer patients who underwent excision of brain metastasis.
 Methods: In each patient we performed molecular analysis of paired archived FFPET specimens from both the PBC and excised BM. Of the 37 pairs of PBC/BM samples, 24 pairs had sufficient pathology material for molecular analysis. Patient characteristics: mean age at PBC diagnosis was 46.7 years (range 27-67 years); 7 (29%) ER+, 17 (71%) ER-, 12 (50%) HER2-positive(3+). We performed cDNA-mediated annealing, selection, extension and ligation (DASL) assay (Illumina Corp) for expression of 502 known cancer genes, using 200 ng RNA. Statistical analysis for microarrays (SAM) accounting for the pairing of the primary and metastasized tumors was used to identify differentially expressed genes while controlling the false discovery rate (FDR <0.01). BeadStudio™ Absolute correlation clustering was used to cluster samples based on their expression profiles.
 Results: In only 7 (29%) cases matched PBC and BM pair clustered together on unsupervised hierarchical clustering, the pairs in remaining cases clustered apart. Comparison of the two groups (PBC and BM) showed that 41 genes were up regulated in BM, including proliferation genes (CDC2, CDC25a, CCNA2 and E2F family), anti-apoptotic (BIRC5), DNA repair (RAD51, -54b, XRCC2, BRCA2, BARD1, TOP1), angiogenesis (VEGF), and development of drug resistance (ABCB1, -G2). In contrast, the 43 genes that were down regulated in BM included those associated with invasion (MMP2, -3, -14), cellular motility, and epithelial to mesenchymal transformation (CDH11). Additional analysis to validate these trends and to identify potential therapeutic targets is underway.
 Conclusions: Although some BM retain remarkable similarity to the PBC, majority exhibit considerable deviation in their gene expression profile. These “adaptive” changes include greater resistance to drug therapy, increased DNA repair, a reversal back to the epithelial phenotype and decreased capacity for cell motility and invasion.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2028.

Predictors of brain relapse in HER-2 positive metastatic breast cancer (MBC) patients (pts)

10508

Background: Brain relapse is a common occurrence in HER2-positive breast cancer pts. We assessed factors determining the risk of this event in a large unselected series of HER2-positive MBC pts. Methods: Study group included 233 consecutive HER2-positive (IH 3+ or FISH+) MBC pts (median age 53 years); 49% premenopausal, 49% postmenopausal and 2% with unknown menopausal status. Dominant site of disease included viscera (78%), soft tissue (11%) and bones (10%). Of the 206 pts (88%) with known steroid receptor status, ER+/PgR+, ER+/PgR-, ER-/PgR+, ER-/PgR- phenotypes included 58%, 15%, 5% and 21% of pts, respectively. Prior (neo)adjuvant chemotherapy, endocrine therapy or a combination thereof was administered in 40%, 6% and 35% of pts, respectively. Disease-free interval to the development of MBC ranged between 0 and 142 months (median 16 months). 184 pts (79%) received trastuzumab for MBC, usually in combination with chemotherapy. Statistical analysis included contingency tables, chi-square test, Kaplan-Meier survival analysis and Cox proportional hazard model. Results: Median follow-up from the development of MBC was 25 months (range 0.5–130 months). 54 pts (23%) developed brain metastases after a median of 13 months (range, 0 to 81 months). Cumulative risk of brain relapse was 11% (95% CI: 7–16%) and 24% (95% CI: 17–32%) at one and two years, respectively. Trastuzumab treatment was associated with insignificantly reduced risk of brain metastases (HR 0.63, 95% CI 0.29–1.39, p = 0.25). In the univariate analysis, premenopausal status was the only significant factor associated with increased risk of brain relapse (HR 2.56, 95% CI 1.28–5.00, p = 0.008). Conclusion: HER-2 positive MBC pts carry high risk of brain relapse, in particular prior to menopause. Protective role of trastuzumab warrants further research.

[Table: see text]

Activity of trastuzumab-based therapy beyond disease progression in heavily pretreated metastatic breast cancer patients—Single institution experience

13159

Background: Benefits from continuing trastuzumab-based (TZB) therapy beyond disease progression in HER-2-overexpressing metastatic breast cancer (MBC) patients (pts) remain obscure. Methods: A retrospective analysis was undertaken to assess activity of TZB therapy for MBC pts treated in our institution from 2002 to 2005 outside clinical trials. Results: 27 pts were evaluated. Median age: 52 years (range, 33–62). 9 pts (33.3%) were premenopausal. Hormonal receptors status: 9 pts ER(+), 4 pts PgR (+), 2 unknown. HER-2 overexpression was determined by IHC staining (3+ score) in all pts. Metastases location: 18 pts soft tissues/bone, 18 pts visceral disease. Median number of metastatic sites: 2 (range: 1–4). 9 pts (33.3%) had metastases in < 2 locations. 16 pts (59.2%) received neo/adjuvant chemotherapy: 11 pts doxorubicin, 8 pts CMF, 2 pts docetaxel, 4 pts other. Median previous chemotherapy lines for advanced disease: 2 (range: 0–6). 16 pts received doxorubicin/epirubicin, 14 pts docetaxel, 13 pts vinorelbine as a part of advanced disease chemotherapy regimen. Trastuzumab was administered at standard doses and combined with docetaxel, vinorelbine, cisplatin, capecitabine, etoposide, gemcitabine or administered as monotherapy. Response for the first-line TZB therapy was as follows: CR 5/27 pts (18.5%); PR 10/27 pts (37%). Median TTP was 5.8 months (range: 0–22). 14/27 pts (51.8%) received a second-line TZB therapy beyond disease progression. Response for the second-line therapy: CR 2/14 pts (14.3%); PR 5/14 pts (35.7%). Median TTP was 5.1 months (range: 0–24). 6/14 pts received a third-line and subsequent lines (up to five lines) of TZB therapy. PR for subsequent lines of therapy was observed in 4 pts. Median survival has not been reached. Pts who received ≥2 of TZB regimens survived significantly longer than pts who had received only 1 regimen (P = 0,02 logrank). Pts with metastasis in 1 location survived significantly longer than pts with metastasis in ≥2 sites (P = 0,01 logrank). Conclusions: Trastuzumab-based therapy seems to be active in MBC pts beyond disease progression even in heavily pretreated population. Durable responses were observed in some cases.

No significant financial relationships to disclose.