Abstract P3-07-09: Quantitative p95HER2 protein expression is predictive of trastuzumab response in HER2-positive metastatic breast cancer

Background: Expression of p95HER2 (p95), a truncated form of the HER2 receptor that lacks the trastuzumab binding site but retains kinase activity, has been reported as a prognostic biomarker for poor outcome in trastuzumab-treated HER2-positive metastatic breast cancer (MBC). However, the ability of p95 to predict trastuzumab benefit has not been demonstrated due to the difficulty in obtaining the appropriate control group, namely HER2+ MBC patients not treated with trastuzumab. In the current study, the predictive value of p95 expression was tested in a cohort comprised of HER2-positive MBC patients treated before the availability of trastuzumab and trastuzumab-treated HER2-positive MBC patients.

Methods: The current cohort was derived from 206 HER2-positive MBC patients in the Munich Cancer Registry with a median follow up of 64 months. Cases were divided between those that received trastuzumab (n=115) and those that were treated before the availability of trastuzumab (n=91). Quantitative p95 protein expression was measured in formalin-fixed paraffin-embedded samples using the p95 VeraTag® assay (Monogram Biosciences), which is specific for the active M611 form of p95. Quantitative total HER2 protein expression was measured using the HERmark® assay (Monogram Biosciences). p95 and HERmark cutoffs were pre-specified (Duchnowska, Clin Cancer Res, 20:2805, 2014 and Huang, Am J Clin Pathol, 134:303, 2010). Analyses with p95 were restricted to samples with confirmed HER2 overexpression by HERmark. All hazard ratios (HR) were stratified by estrogen receptor status and grade.

Results: Consistent with previous training (Sperinde, Clin Cancer Res, 16:4226, 2010) and validation (Duchnowska, Clin Cancer Res, 20:2805, 2014) datasets, subjects treated with trastuzumab experienced a shorter time to progression (TTP) when p95 expression levels were above the cutoff versus below the cutoff (HR = 3.8, p = 0.019). However, only a trend was observed between p95 expression levels and overall survival (HR = 2.2, p = 0.20), possibly due to a lower frequency of events and relatively small sample size. The predictive value of p95 was assessed by determining the benefit of adding trastuzumab to chemotherapy treatment in subsets below and above the p95 cutoff. As expected, patients with p95 below the cutoff experienced significant benefit in TTP from adding trastuzumab (HR = 0.13, p<0.001), whereas patients with p95 above the cutoff experienced less benefit (HR = 0.70, p=0.47). p95 expression level was predictive of trastuzumab response with an interaction p-value of 0.015. The results for OS were similar, however trastuzumab benefit was less distinct between the two groups (interaction p = 0.18); HR = 0.23, p = 0.0013 below the p95 cutoff versus HR = 0.50, p = 0.14 above the p95 cutoff.

Conclusions: In this dataset, quantitative p95 expression was predictive of trastuzumab treatment benefit in MBC. Patients with high p95 expression may be particularly good candidates for dual HER2 blockade, as reported in the NeoALTTO trial (Scaltriti, Clin Cancer Res, 21:569, 2015), or other additional therapies.

Citation Format: Sperinde J, Bachmeier B, Weidler JM, Lie Y, Chenna A, Winslow J, Engel J, Schubert-Fritschle G, Sommerhoff C, Petropoulos C, Bates M, Huang W, Nerlich A. Quantitative p95HER2 protein expression is predictive of trastuzumab response in HER2-positive metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-09.

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.

Abstract P2-10-31: Correlation of quantitative p95HER2 and total HER2 levels with clinical outcomes in a combined analysis of two cohorts of trastuzumab-treated metastatic breast cancer patients

Background: Expression of p95HER2 (p95), a truncated form of HER2 also known as p110 or M611-CTF, is a possible trastuzumab resistance mechanism and has been associated with poor prognosis in trastuzumab-treated HER2-positive metastatic breast cancer (MBC). Previously we reported on optimal clinical cutoffs for quantitative p95 (Clin Cancer Res, 16:4226, 2010) and quantitative HER2 protein expression (H2T) by HERmark® (Cancer, 116:5168, 2010) that defined patient subsets with different progression-free survival (PFS). These cutoffs were confirmed in an independent trastuzumab-treated MBC cohort (ASCO 2011, #586). Here, using individual patient data, we performed an analysis on the combined data set of 243 cases from the discovery and validation cohorts to derive optimal cutoffs for quantitative p95 and H2T.

Methods: Both quantitative H2T (HERmark, Monogram Biosciences) and p95 assays employed the VeraTag® method to quantify protein expression in formalin-fixed, paraffin-embedded tumor samples from two cohorts of 101 and 142 cases of trastuzumab-treated MBC with 7.4 and 9.2 months median PFS, respectively. All analyses were stratified by hormone receptor status, tumor grade (3 vs. 1+2) and cohort. H2T measurements were compared to pre-specified cutoffs for HERmark negative (H2T<10.5 Relative Fluorescence/mm2 tumor [RF/mm2]) and HERmark positive (H2T>17.8 RF/mm2), derived from the <5th percentile of centrally determined HER2-positives and the >95th percentile of centrally determined HER2-negatives, respectively, within a reference database of 1,090 breast cancer patient samples.

Results: Patients classified as HERmark-positive had longer PFS than those classified as HERmark-negative (HR = 0.52; p = 0.0006; medians 10.0 and 5.9 months). The previously determined optimal H2T cutoff of 13.8 RF/mm2 in the center of the HERmark-equivocal zone, gave a similar result (HR = 0.54; p = 0.0005). This was close to the optimal cutoff of 12.75 RF/mm2 (HR = 0.48; p < 0.0001, unadjusted) for the combined data set. The PFS for the small group of patients in the HERmark-equivocal zone (n = 20) was more similar to the HERmark-negatives (equivocal vs. negative: HR=0.98; p = 0.9) than the HERmark-positives (positive vs. equivocal: HR=0.57; p = 0.057). The pre-specified p95 cutoff at 2.8 RF/mm2 separated the 174 HERmark-positive cases into two groups of longer (p95<2.8 RF/mm2) vs. shorter PFS (HR = 1.9; p = 0.0014; medians 13.1 and 7.4 months). Increasing continuous p95 also correlated with shorter PFS (HR = 1.9/log; p = 0.022) in the HERmark-positive subset. An optimal p95 cutoff was identified at 2.7 RF/mm2 (HR = 2.0; p = 0.0009, unadjusted), although a slightly higher local HR maximum was found at 1.55 RF/mm2 (HR = 2.3; p = 0.0004, unadjusted).

Conclusions: HERmark positive and negative categories, defined by analytical comparison with centrally determined HER2 status, were confirmed to have significantly different PFS in trastuzumab-treated MBC patients. The optimal H2T clinical cutoff for this combined analysis was centered in the HERmark analytical equivocal zone. An optimal p95 clinical cutoff of 2.7 RF/mm2 derived from this combined analysis was nearly identical to the previously established cutoff of 2.8 RF/mm2.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-31.

Abstract P2-05-06: Quantitative measurement of HER2 expression in breast cancers: comparison with “real world” HER2 testing in a multi-center Collaborative Biomarker Study (CBS) and correlation with clinicopathological features

Background: Accurate determination of HER2 status is critical in determining appropriate therapy for breast cancer patients. The HERmark® assay is a novel method to quantitatively measure HER2 total protein expression (H2T) in breast cancer. In this study, we compared HERmark H2T with central laboratory HER2 retesting and local (site reported) HER2 testing of formalin-fixed, paraffin-embedded (FFPE) breast cancer tissues. The quantitative total HER2 measurements (H2T) by HERmark and results of local HER2 tests were correlated with tumor pathohistological characteristics and overall survival of breast cancer patients.

Methods: 232 FFPE breast cancer tissues were provided by 11 CBS study sites for HER2 testing by the HERmark assay and central laboratory IHC re-testing performed in blinded fashion. Local HER2 immunohistochemistry and/or fluorescence in situ hybridization (FISH) results and valid HERmark H2T and central HER2 IHC results were obtained in 192 cases for analysis.

Results: H2T showed a significant correlation with central HER2 IHC staining intensity (P < 0.0001). The concordance rates of positive and negative HERmark status (excluding equivocal) with those of local HER2 status determined by the CBS sites, and with those of central HER2 IHC status were 84% (Kappa = 0.68) and 96% (Kappa = 0.91), respectively. Higher H2T levels significantly correlated with higher tumor grade (p = 0.007) and negative ER/PR status (p = 0.002). Twenty-six (14%) cases showed discordant (conversion of negative and positive) results between local HER2 status and HERmark status. Of the discordant cases, HERmark significantly agreed with H-score of central HER2 IHC retesting (p = 0.014), as compared with local HER2 status. The concordant negative group (local HER2 negative/H2T low) demonstrated better overall survival (OS) (HR = 0.198, p = 0.0001), compared to that of concordant positive group (local HER2 positive/H2T high). The concordant negative group also showed better OS than that of discordant local HER2 negative/H2T high group (HR = 0.065, p = 0.0003), but showed no significant difference in OS as compared to that of discordant local HER2 positive/H2T low group (HR = 1.774, p = 0.499).). In 24 cases (13%) considered to be “triple negative” by local HER2, ER and PR testing, HERmark re-classified 4 cases (17%) as HER2 positive.

Conclusions: H2T by HERmark yields a continuum of quantitative HER2 protein measurements that shows an excellent correlation with central HER2 IHC retesting and confirms the known correlations between HER2 expression with tumor grade and ER/PR status. OS results of concordant HER2 positive or negative groups (between local HER2 testing and HERmark H2T) confirmed that HER2 positive patients (excluding adjuvant trastuzumab therapy) have worse OS than patients with HER2 negative disease. However, in the HERmark and local HER2 discordant groups, OS appeared to track better with H2T by HERmark and not with the local HER2 status. Novel quantitative HER2 measurements may identify patients with false (+) and (−) HER2 status by local HER2 testing and may provide added clinical value to routine “real world” HER2 testing.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-05-06.

Abstract P2-10-16: Quantitative HER3 protein expression and PIK3CA mutation status in matched samples from primary and metastatic breast cancer tissues and correlation with time to recurrence

Background: HER3 is thought to play a prominent role in resistance to HER2-directed breast cancer therapies. Recent data suggest that HER3 levels also influence HER2-normal breast tumor biology. HER3 and PI3K signaling are linked in that in HER3 signaling activates PI3K and inhibition of PI3K activity can upregulate HER3 expression. Here, we measured quantitative HER3 protein expression levels and PIK3CA mutation status in matched tissues from the primary tumor and site of metastasis to assess correlations with time to recurrence.

Methods: 44 pairs (8 HER2+ by HERmark®) of matched tissues from the primary tumor and the site of metastasis were evaluated for HER3 protein expression using a sensitive, quantitative assay for HER3 protein expression in FFPE tissue sections (VeraTag®). Matched samples were also evaluated for quantitative HER2 expression (HERmark) and for PIK3CA mutations at exon 9 (E542K and E545K) and exon 20 (H1047R).

Results: HER3 protein expression at the metastatic site was largely independent of HER3 levels at the primary site (Spearman p = 0.50) in contrast to HER2 expression (Spearman p = 0.0004). HER3 expression in the primary tumor correlated with time to recurrence (TTR) (HR = 2.0 per 2-fold increase in HER3; p < 0.0001). Conversely, HER3 expression measured at the site of metastasis was not correlated with TTR (p = 0.55). Estrogen receptor negative tumors were less likely to have PIK3CA mutations (p = 0.023). In cases of primary tumors with PIK3CA mutations, no reversions to wild-type PIK3CA were observed in the metastatic sites. In metastatic tumors, mutations detected in the primary tumor as well as new mutations were observed. A gain of an exon 9 mutation at the metastatic site correlated with shorter TTR (HR = 2.5; p = 0.043). Excluding the 8 samples that were HER2+ by HERmark, longer TTR was observed for patients with PIK3CA mutations in the primary tumor (HR = 0.47; p = 0.042), which is consistent with previous reports. Interestingly, the longer TTR for those with PIK3CA mutations appeared to be dependent on quantitative HER3 protein level (interaction p = 0.065).

Conclusions: HER3 protein expression in matched primary and metastatic breast cancer tissues were unrelated. This may indicate that HER3 protein is influenced by the different tumor microenvironments of the primary and metastatic sites. PIK3CA mutations were either maintained or acquired at metastatic sites. Both low HER3 protein expression and the presence of PIK3CA mutations in the primary tumor but not the metastatic tumor were associated with longer TTR. These observations suggest that HER3 protein expression may be an important prognostic factor for breast cancer progression.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-16.

Predictive value of HIV-1 replication capacity and phenotypic susceptibility scores in antiretroviral treatment-experienced patients

OBJECTIVES

The aim of the study was to determine the prognostic value of HIV replication capacity (RC) for subsequent antiretroviral (ARV) treatment response in ARV-experienced patients.

METHODS

RC and phenotypic resistance testing were performed at baseline and week 12 on plasma samples from patients randomized to undergo a 12-week ARV drug-free period (ARDFP) or initiate immediate salvage therapy (no-ARDFP group) in the Options in Management with Antiretrovirals (OPTIMA) trial. Dichotomous and incremental phenotypic susceptibility scores (dPSSs and iPSSs, respectively) were calculated. The predictive value of RC and PSS for ARV therapy response and/or ARDFP was evaluated using multivariate regression analysis and Pearson correlations.

RESULTS

In 146 no-ARDFP subjects, baseline RC (50.8%) did not change at week 12 and was not correlated with CD4 cell count or viral load changes at week 12 (P=0.33 and P=0.79, respectively) or at week 24 (P=0.96 and P=0.14, respectively). dPSS predicted virological but not CD4 cell count response to ARV therapy at weeks 12, 24 and 48 (P=0.002, P<0.001 and P=0.005, respectively). RC was significantly correlated with dPSS and iPSS at baseline, but did not increase their predictive value. In the 137 ARDFP patients, RC increased significantly (from 52.4 to 85.8%), but did not predict CD4 cell count and viral load changes during ARDFP (P=0.92 and P=0.26, respectively). RC after ARDFP did not predict subsequent CD4 cell count and viral load changes 12 weeks following ARV treatment reinitiation (P=0.90 and P=0.29, respectively).

CONCLUSIONS

We found no additional predictive value of replication capacity for virological or immunological responses (above what PSS provides) in patients undergoing salvage ARV treatment.

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.

P1-07-12: Assessment of Real World HER2 Status by Immunohistochemistry (IHC) and Fluorescence In Situ Hybridization (FISH) in Breast Cancers: Comparison with HERmark®, a Validated Quantitative Measure of HER2 Protein Expression

Background: Accurate assessment of the HER2 status is critical in determining appropriate therapy for patients with invasive breast cancer. ASCO/CAP HER2 testing guidelines caution that up to 20% of routine HER2 testing by IHC/FISH may be unreliable (Wolff et al. JCO 2007;25:118). The HERmark assay is a novel quantitative HER2 protein measurement for determining HER2 status in breast cancer. Central HER2 testing showed high concordance (96-98%) with HERmark for positive and negative categories when equivocal subsets were excluded (Huang et al. Am J Clin Pathol 2010;134:303; Joensuu et al, 2008 SABCS, abstract 2071). In this study, we examined concordance between HERmark and routine HER2 testing by IHC and FISH from “real world” formalin-fixed, paraffin-embedded (FFPE) breast cancers submitted commercially for HERmark testing.

Methods: 717 HERmark results on FFPE breast cancers tested from 2008 to 2010 and corresponding HER2 IHC/FISH results were reviewed. The IHC and FISH results, per pathology reports submitted at the time of HERmark testing, were compared to HERmark categorical (negative, equivocal, positive) results.

Results: 590 (419) samples had IHC (FISH) and HERmark results available. Of these cases, 92% (94%) were either negative or equivocal by IHC (FISH). The HERmark testing reported 33% HERmark negative, 33% HERmark equivocal and 34% HERmark positive. Comparisons of HER2 status by IHC and FISH vs. HERmark are detailed in Table 1.

P1-07-01: Comparison of Four HER2 Testing Methods in the Detection of HER2−Positive Breast Cancer: Results from the FinHer Study Cohort

Background: Accurate assessment of the HER2 status is essential for identifying patients who may benefit from HER2 targeted therapy. The current methods, immunohistochemistry (IHC) and in situ hybridization (ISH), determine HER2 status semi-quantitatively as positive (+), equivocal (+/−) and negative (−) with predefined cutoff values. Recent studies have suggested that current HER2 cutoffs may not be optimal for all clinical settings of HER2 targeted therapy. In a small subset of adjuvant NCCTG N9831 patients confirmed as HER2−normal by round-robin review of HER2 testing, trastuzumab benefit was observed (Perez et al, SABCS 2010). Quantification of HER2 as continuous variable may enable a more accurate optimization of HER2 cutoffs for various HER2 targeted therapies. In this study, we measured continuous HER2 protein expression by the HERmark™ assay and continuous mRNA expression by quantitative real time polymerase chain reaction (qPCR), and compared these results with central IHC and central chromogenic in situ hybridization (CISH) results of FinHer.

Methods: Total HER2 protein expression (H2T) was quantified using the HERmark assay as previously described (Huang et al. Am J Clin Pathol 2010;134:303). HER2 mRNA expression (H2N) was measured by qPCR as previously published (Noske et al. Br Cancer Res Treat 2011;126:109). The results of H2T and H2N as continuous variables and as predefined categories were compared with central CISH results from FinHer (Joensuu et al, N Engl J Med 2006;354), and central IHC retesting.

Results: H2T in 899 evaluable samples described a continuum of 0.4 to 721.2 (relative HERmark unit); while H2N in 915 evaluable samples showed a continuum of 31.4 to 42.8 (delta-Ct). Significant correlation between H2T and H2N as continuous variable was found (R2= 0.56, P&lt; .0001). Paired method comparison was performed for samples with valid results in any two of the four testing methods. Overall concordance of H2T and H2N with predefined categories (+, +/−, -) was 81%, and concordance of (+) and (−) subsets was 95% when (+/−) cases (H2T 11%; H2N 6%) were excluded. Overall concordance of central IHC and H2T categories (+, +/−, -) was 75%, and concordance of (+) and (−) subsets was 96% when (+/−) cases (IHC 16%; H2T 11%) were excluded. Overall concordance of IHC and H2N categories (+, +/−, -) was 84%, and concordance of (+) and (−) subsets was 99% when (+/−) cases (IHC 16%; H2N 6%) were excluded. Concordance of central CISH (+, -) with H2T and H2N categories (+, -) was 89% and 91%, respectively, when (+/−) cases were excluded from H2T (13%) and H2N (8%), respectively.

Conclusions: All four methods identified HER2−positive breast cancers. The discordance rate between the methods tested was approximately 10 to 20% despite careful delineation of cancerous tissue in the sample and analysis of adjacent tumor sections. No combination of assays could be identified with concordance rate &gt;95% when the equivocal subsets were included in comparisons. Exclusion of the equivocal subsets (about 10% of samples) yielded high concordance rates of approximately 95% or higher. H2T and H2N showed comparable continuous distribution patterns and significant concordance with standard HER2 status by central IHC and CISH.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-07-01.

Identification of a subpopulation of metastatic breast cancer patients with very high HER2 expression levels and possible resistance to trastuzumab

BACKGROUND

Patients with metastatic breast cancer (MBC) overexpressing HER2 (human epidermal growth factor receptor 2) are currently selected for treatment with trastuzumab, but not all patients respond.

PATIENTS AND METHODS

Using a novel assay, HER2 protein expression (H2T) was measured in formalin-fixed, paraffin-embedded primary breast tumors from 98 women treated with trastuzumab-based therapy for MBC. Using subpopulation treatment effect pattern plots, the population was divided into H2T low (H2T < 13.8), H2T high (H2T ≥ 68.5), and H2T intermediate (13.8 ≤ H2T < 68.5) subgroups. Kaplan-Meier (KM) analyses were carried out comparing the groups for time to progression (TTP) and overall survival (OS). Cox multivariate analyses were carried out to identify correlates of clinical outcome. Bootstrapping analyses were carried out to test the robustness of the results.

RESULTS

TTP improved with increasing H2T until, at the highest levels of H2T, an abrupt decrease in the TTP was observed. KM analyses demonstrated that patients with H2T low tumors [median TTP 4.2 months, hazard ratio (HR) = 3.7, P < 0.0001] or H2T high tumors (median TTP 4.6 months, HR = 2.7, P = 0.008) had significantly shorter TTP than patients whose tumors were H2T intermediate (median TTP 12 months). OS analyses yielded similar results.

CONCLUSIONS

MBC patients with very high levels of H2T may represent a subgroup with de novo resistance to trastuzumab. These results are preliminary and require confirmation in larger controlled clinical cohorts.

Discordant HER2 Total and HER2 Homodimer Levels by HERmark Analysis in Matched Primary and Metastatic Breast Cancer FFPE Specimens

Background: HER-2/neu is over-expressed in approximately 25% of primary invasive breast cancers and selection of patients for consideration of trastuzumab is a critical step in defining the treatment plan. We have previously reported that quantitative measurements of HER2 protein expression (H2T) and HER2 homodimers (H2D) using the HERmark assay identifies sub-populations of “HER2-positive” patients (by IHC and/or FISH) that have different clinical outcomes on trastuzumab (Leitzel, ASCO 2008; Lipton, SABCS 2008). Previous studies report up to a 20 % discordance in HER2 status using conventional IHC or FISH analysis between the primary and metastatic breast tumors. Here we correlate HER2 total and homodimer levels in matched primary and metastatic tissue from the same patient.Methods: 27 patients had matched primary and metastatic FFPE (formalin-fixed, paraffin-embedded) specimens tested in the HERmark assay to quantitate and compare their H2T and H2D expression levels.Results: FFPE tissue was available from 27 primary breast cancers and metachronous metastatic sites. Metastatic lesions included 7 skin, 5 lymph node, 3 bone, 3 pleura, 2 brain, 2 chest wall, and 5 other soft tissue lesions. The median elapsed time between matched primary and metastatic sites was 71 mo. (range 9-137 mo). During the time period between the primary specimen harvest and the metastatic biopsy, 6 patients were treated with chemotherapy alone, 10 received hormonal therapy without trastuzumab, 3 patients received trastuzumab, and 3 received no treatment. Treatment was not known for 5 patients. For the whole population, there was a weak to moderate positive correlation between primary and metastatic cancers with H2T (r2=0.36, p&lt;0.001) and for H2D (r2=0.27, p&lt;0.006). Using the optimized time to progression (TTP) positional scanning cutpoints for H2T and H2D defined in our previous reports, 4/20 patients (20%) converted from low to high, and 1/7 (14%) converted from high to low H2T. Using the H2D cutpoint, 7/15 patients (47%) converted from low to high, and 3/12 (25%) converted from high to low H2D. Overall discordance between primary and metastatic sites was 19% for H2T, and 37% for H2D.Conclusions: HERmark analysis of matching primary and metastatic breast cancers revealed 19% discordance for H2T, and 37% for H2D. The most frequent conversion was from low HER2 in the primary tissue to high HER2 in the metastatic site.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2131.

Correlation of quantitative total HER2 expression and HER2 homodimers with histopathologic characteristics of breast cancers in the FinHer study

11061

Background: We recently reported that the HERmark assay (Monogram Biosciences) accurately measures continua of total HER2 expression (H2T) and HER2 homodimers (H2D) over a wide (∼3 logs) dynamic range, and that a higher concordance was observed between H2T and HER2 status with more stringent central tests as compared with IHC tests performed locally (Joensuu et al, 2008 SABCS,abstract 2071). H2D/H2T ratio was reported as a marker of activated HER2 and a prognosticator of disease progression in HER2+ patients not treated with trastuzumab in the adjuvant setting (Bates et al, 2008 SABCS,abstract 1074). In this follow-up analysis, H2T, H2D, and H2D/H2T ratio were correlated with histopathologic characteristics of breast cancers in the FinHer study. Methods: The HERmark assay was used to measure H2T and H2D in 899 formalin-fixed, paraffin-embedded FinHer specimens. The results were correlated with histopathologic characteristics of breast cancers in the FinHer study (Joensuu et al, N Engl J Med2006;354), including estrogen receptor/progesterone receptor (ER/PR), tumor grade, tumor size, lymph node metastasis, and stage. Results: Higher H2T and H2D levels correlated with ER/PR negativity and high tumor grade (P<0.0001). 42% (102/244) of ER- and 37% (137/374) of PR- cases were HERmark Positive; while 17% (110/655) of ER+ and 14% (75/524) of PR+ cases were HERmark Positive. 10% (13/136) of grade 1, 18% (65/353) of grade 2, and 35% (131/375) of grade 3 tumors were HERmark Positive. No significant association was found between H2T or H2D and tumor size, lymph node metastasis or stage. ER/PR negative and poorly differentiated cancers had higher H2D/H2T ratios (P=0.013), and H2D/H2T ratios >0.6 were associated with smaller primary tumor diameters at the time of cancer detection (P=0.009). Conclusions: The quantitative H2T measurement confirms the known correlations between HER2 expression and histopathologic characteristics of breast cancer. The novel H2D measurement and H2D/H2T ratio may provide further insights into HER2 activation and better diagnostic tests for targeted HER2 therapy.

[Table: see text]

Randomised comparison of the Classic Laryngeal Mask Airway with the Cobra Perilaryngeal Airway during anaesthesia in spontaneously breathing adult patients

We tested the hypothesis that the Cobra Perilaryngeal Airway (PLA) with its high volume low-pressure cuff would provide superior airway leakage pressure compared with the Classic Laryngeal Mask Airway (LMA) in spontaneously breathing adult patients. Ninety consecutive adult patients were randomly allocated to receive one of these two supralaryngeal devices. The airway leakage pressure was higher for the PLA compared with the LMA (22 +/- 9 cmH2O vs. 18 +/- 6 cmH2O; P < 0.05). The mean airway device intracuff pressure was lower for the PLA compared to the LMA (36.1 +/- 15.2 mmHg vs. 86.3 +/- 25.3 mmHg P < 0.0001). The time required to achieve successful insertion was greater for the PLA compared with the LMA (39 +/- 21 seconds vs. 27 +/- 10 seconds; P < 0.005). The number of attempts required to achieve successful insertion and the incidence of postoperative complications were similar in both groups. The findings suggest that the PLA provides a superior airway seal at a lower intracuff pressure compared to the LMA. However the time for successful insertion may be increased.

Quantitative measurements of HER2 expression and HER2 homodimer using a novel proximity based assay: comparison with HER2 status by immunohistochemistry and chromogenic in situ hybridization in the FinHer study

Abstract #2071

Background: The accuracy and reliability of current methods, immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), to assess HER2 status has recently been a subject of debate. The best method to assess HER2 status remains controversial. We developed a novel assay (HERmark, Monogram Biosciences) that provides precise quantification of HER2 expression (H2T) and HER2 homodimer (H2D) in formalin-fixed paraffin-embedded (FFPE) tissues. We compared H2T and H2D to local IHC, central chromogenic in situ hybridization (CISH) and central IHC retesting of breast cancers from the FinHer study.&#x2028; Methods: H2T and H2D were detected through light-dependent release of fluorescent tags (VeraTag reporters) conjugated to a HER2 antibody, requiring proximity to a second HER2 “scissors” antibody. The VeraTag signal was quantified by capillary electrophoresis and normalized to tumor area. Assay comparisons correlated H2T and H2D with HER2 testing by local IHC and central CISH from FinHer (Joensuu et al, N Engl J Med 2006;354), as well as central HER2 status reassessment by combination of externally performed central IHC retesting (PhenoPath labs, Seattle, WA) and central CISH (FinHer) according to ASCO/CAP guideline for HER2 testing in breast cancer (Wolff et al, Arch Pathol Lab Med 2007;131).&#x2028; Results: H2T and H2D in 899 evaluable FinHer samples described a continuum over a wide dynamic range (∼ 3 logs), in contrast with conventional IHC categories (0-3+). The correlation between H2T and IHC categories was significant (P &lt; .0001). Overlap of H2T among the IHC categories was observed. H2D showed a similar correlation with IHC and a general correlation with H2T (P &lt; .0001). A H2T cutoff value, based on its ability to distinguish high and low responders in a cohort of metastatic breast cancer patients treated with trastuzumab-based regimens (log10 H2T= 1.14, Leitzel et al, 2008 ASCO, abstract 1002), was used to define HERmark negative (-) and positive (+), which were then compared with IHC and CISH results. The concordances between HERmark (-) and local IHC (-), central CISH (-), and central HER2 reassessment (-) were 89%, 84%, and 91%, respectively. The concordances between HERmark (+) and local IHC (+), central CISH (+), and central HER2 reassessment (+) were 71%, 89%, and 92%, respectively. The HERmark test showed greater overall concordance with central HER2 reassessment (91%) than with local IHC (84%) and central CISH (87%)&#x2028; Conclusions: HERmark reliably measures H2T and H2D in FFPE tissues. H2T showed excellent concordance with central HER2 status according to ASCO/CAP guideline for HER2 testing. The precise quantification of H2T and H2D may provide novel, quantifiable, predictive tests for targeted HER2 therapy.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2071.

Antiviral activity and cross-resistance profile of P-1946, a novel human immunodeficiency virus type 1 protease inhibitor

The HIV protease inhibitor P-1946 is a member of a novel family of l-Lysine derivatives. The compound is a specific HIV-1 protease inhibitor that has potent and selective in vitro antiviral activity (EC50 152 nM) against a range of isolates resistant to commercially available protease inhibitors. The presence of at least four primary and four secondary drug resistance mutations is required to achieve greater than four-fold resistance to P-1946. P-1946's favorable resistance profile makes it a good lead for the development of new agents active against existing PI-resistant virus in treatment-experienced patient.