Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

INTRODUCTION

The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures.

METHODS

In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025.

FINDINGS

Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2-6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p<0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5-5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p<0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4-10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p<0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32-4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP >5mg/L, OR 3·55 [1·23-11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation.

INTERPRETATION

After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Safety and efficacy of tenecteplase in patients with wake-up stroke assessed by non-contrast CT (TWIST): a multicentre, open-label, randomised controlled trial

BACKGROUND

Current evidence supports the use of intravenous thrombolysis with alteplase in patients with wake-up stroke selected with MRI or perfusion imaging and is recommended in clinical guidelines. However, access to advanced imaging techniques is often scarce. We aimed to determine whether thrombolytic treatment with intravenous tenecteplase given within 4·5 h of awakening improves functional outcome in patients with ischaemic wake-up stroke selected using non-contrast CT.

METHODS

TWIST was an investigator-initiated, multicentre, open-label, randomised controlled trial with blinded endpoint assessment, conducted at 77 hospitals in ten countries. We included patients aged 18 years or older with acute ischaemic stroke symptoms upon awakening, limb weakness, a National Institutes of Health Stroke Scale (NIHSS) score of 3 or higher or aphasia, a non-contrast CT examination of the head, and the ability to receive tenecteplase within 4·5 h of awakening. Patients were randomly assigned (1:1) to either a single intravenous bolus of tenecteplase 0·25 mg per kg of bodyweight (maximum 25 mg) or control (no thrombolysis) using a central, web-based, computer-generated randomisation schedule. Trained research personnel, who conducted telephone interviews at 90 days (follow-up), were masked to treatment allocation. Clinical assessments were performed on day 1 (at baseline) and day 7 of hospital admission (or at discharge, whichever occurred first). The primary outcome was functional outcome assessed by the modified Rankin Scale (mRS) at 90 days and analysed using ordinal logistic regression in the intention-to-treat population. This trial is registered with EudraCT (2014-000096-80), ClinicalTrials.gov (NCT03181360), and ISRCTN (10601890).

FINDINGS

From June 12, 2017, to Sept 30, 2021, 578 of the required 600 patients were enrolled (288 randomly assigned to the tenecteplase group and 290 to the control group [intention-to-treat population]). The median age of participants was 73·7 years (IQR 65·9-81·1). 332 (57%) of 578 participants were male and 246 (43%) were female. Treatment with tenecteplase was not associated with better functional outcome, according to mRS score at 90 days (adjusted OR 1·18, 95% CI 0·88-1·58; p=0·27). Mortality at 90 days did not significantly differ between treatment groups (28 [10%] patients in the tenecteplase group and 23 [8%] in the control group; adjusted HR 1·29, 95% CI 0·74-2·26; p=0·37). Symptomatic intracranial haemorrhage occurred in six (2%) patients in the tenecteplase group versus three (1%) in the control group (adjusted OR 2·17, 95% CI 0·53-8·87; p=0·28), whereas any intracranial haemorrhage occurred in 33 (11%) versus 30 (10%) patients (adjusted OR 1·14, 0·67-1·94; p=0·64).

INTERPRETATION

In patients with wake-up stroke selected with non-contrast CT, treatment with tenecteplase was not associated with better functional outcome at 90 days. The number of symptomatic haemorrhages and any intracranial haemorrhages in both treatment groups was similar to findings from previous trials of wake-up stroke patients selected using advanced imaging. Current evidence does not support treatment with tenecteplase in patients selected with non-contrast CT.

FUNDING

Norwegian Clinical Research Therapy in the Specialist Health Services Programme, the Swiss Heart Foundation, the British Heart Foundation, and the Norwegian National Association for Public Health.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

692 A Machine Learning Approach to Predict the Postoperative Length of Stay After Coronary Artery Bypass Grafting Using Preoperative Characteristics

Aim

Lengthy hospital length of stay (LOS) has a direct impact on healthcare costs. We aimed to design predictive models of prolonged LOS after coronary artery bypass grafting (CABG) with only preoperative characteristics and machine learning (ML) strategies.

Method

In a single centre retrospective analysis, 2,082 consecutive patients underwent first-time elective/urgent CABG: 1,262 has a short postoperative LOS (≤ 6 days) while the remaining 820 had a long LOS (&gt; 6 days). 70/30 training/testing ratio and resampling methods were used, and cross-validation was conducted.

Results

The two groups differ significantly in terms of pre-operative variables: short LOS patients were younger (p &lt; 0.01), more frequently male (p &lt; 0.01) with lower BMI (p &lt; 0.01) and better angina class (p &lt; 0.01) and NYHA class (p &lt; 0.01). Moreover, they had lower incidence of hypertension (p = 0.04), COPD (p &lt; 0.01) and PVD (p &lt; 0.01). The Logistic Euroscore was also better in this group (median 0.02 vs 0.03, p &lt; 0.01). The predictive abilities of the ML models were as follows: logistic regression: Area under the Curve (AUC) = 0.71, accuracy = 0.69; Generalized additive model: AUC= 0.7, Accuracy = 0.68; Random Decision Forest: AUC = 0.7, Accuracy = 0.68; Naïve Bayes AUC = 0.63, Accuracy 0.58.

Conclusions

Developing a reliable predictive model with only pre-operative variables proved to be difficult, but several preoperative characteristics have a significant impact on the probability of prolonged LOS after CABG. Larger studies are needed to investigate the possibility of developing a reliable predictive model that would help to improve surgical planning.

P425Single procedure pace and ablate. evaluation of efficacy and safety comparing three different vascular routes

Funding Acknowledgements

No financial support for this study

Introduction

Permanent pacemaker implantation combined with AVN ablation is a well-established treatment for rate control in patients with atrial fibrillation refractory to medical therapy. At the same sitting, this has been achieved in a single procedure via the subclavian vein (SCV) for both pacemaker implantation and AVN ablation, by pacemaker implantation via the SCV with femoral access for AVN ablation or by using the femoral vein (FV) for leadless pacemaker implantation and AVN ablation with a coaxial single-puncture technique.

We evaluated all combined procedures (pacemaker implantation and AVN ablation at the same sitting) performed in a single centre over 9 years comparing clinical outcomes, complications rates and procedure times.

Statistical methods: 

Continuous variables are described as mean ± standard deviation (SD), and statistical differences between groups were evaluated by one-way ANOVA. A X2 test was used for categorical variables, with Fisher’s exact test for any field where the expected frequency was ≤5 with pvalue &lt; 0.05 considered as statistically significant. The statistical analysis was performed using SPSS software package. 

Results

 

141 patients underwent AVN ablation at our institution as part of a ‘pace and ablate’ single procedure strategy between 14/2/11 and 10/6/19. 61 patients had a combined procedure via the SCV, 66 patients had pacemaker implanted via the SCV and AVN ablation via the FV in the same sitting and 14 patients had leadless pacemaker (Micra) implantation and AVN ablation via the FV. Our findings suggest that the fluoroscopy time as well as the total catheter laboratory time were much less in the Micra group compared to the other groups. In the conventional pacemaker groups (group 1 and 2), the fluoroscopy time was not statistically different between the two. There was a trend towards acute procedural failure, switching to another access as well as a higher complication rate in the SCV group, however this has not reached statistical significance. 

Conclusion

 

Our early data suggests that pacemaker implantation and AVN ablation with a coaxial single femoral vein puncture technique is safe and takes less fluoroscopy time as well as total laboratory time.

Procedural outcomes All (n = 141) Group 1: SCV (n = 61) Group 2: FV (n = 66) Group 3: Micra (n = 14) P-value Total cath-lab time (mins) 113.1 ± 40.4 106.2 ± 37.2 125.7 ± 42.5 86.9 ± 23.1 0.001 Total fluoroscopy time (mins) 8.8 ± 7.6 11 ± 7.8 7.7 ± 7.6 4.5 ± 3 0.0001 Acute procedural failure, n (%) 9 (6.4) 7 (11.5) 2 (3) 0 (0) **0.6 Complications, n (%) 7 (4.9) 5 (8.2) 2 (3) 0 (0) **0.62 **Fisher"s exact test applied to analysis of Micra VS Other methods

P1115Cardiac SABR for ventricular tachycardia - initial UK experience

OnBehalf

United Kingdom Cardiac SABR consortium

Background

Stereotactic Ablative Body Radiotherapy (SABR) is a novel non-invasive treatment for Ventricular Tachycardia (VT) refractory to standard catheter ablation. 3 UK hospitals have started compassionate use cardiac SABR programmes, and are working in close collaboration.

Purpose

To report initial UK experience for treatment of refractory VT with cardiac SABR.

Methods

All patients had undergone prior unsuccessful invasive ablation with VT recurrence despite anti-arrhythmic drug (AAD) use. High-resolution CT imaging with 3D reconstruction was combined with 12 lead ECGs of VT and prior invasive +/- non-invasive electrophysiology mapping data to define a cardiac target. Treatment margins were modified to account for cardiac/respiratory motion and to minimise off target treatment to other organs as per clinical SABR practice. Single fraction high dose treatment (20-25 Gy) was delivered by CT guided Linear Accelerator. Patients were assessed regularly with clinical review and remote device monitoring.

Results

3 patients have been treated so far with aetiologies of prior myocarditis, non-ischaemic dilated cardiomyopathy and ischaemic cardiomyopathy. All patients successfully received planned SABR treatment in &lt;1 hour with no peri-procedural complications. Current follow up is to 4 months. Clinical course was variable – patient 1 had a flare of VT post-SABR requiring temporary escalation of AADs before VT was suppressed, patient 2 had initial suppression of VT but died from decompensated heart failure with further VT after 4 weeks, patient 3 had further VT with a different exit site and underwent repeat invasive ablation and escalated AAD use to achieve VT suppression.

Conclusions

Cardiac SABR shows promise for VT control, but further experience and trials are needed. Integration of imaging and electrophysiology data to generate accurate targets appears critical. The effect of SABR seems to develop over several weeks after therapy. Patient selection and timing of SABR delivery is important with acknowledgement that competing causes of death exist in patients with refractory VT entering a compassionate use program.

Abstract Figure. Example SBRT plan

Multiplex profiling identifies clinically relevant signalling proteins in an isogenic prostate cancer model of radioresistance

The exact biological mechanism governing the radioresistant phenotype of prostate tumours at a high risk of recurrence despite the delivery of advanced radiotherapy protocols remains unclear. This study analysed the protein expression profiles of a previously generated isogenic 22Rv1 prostate cancer model of radioresistance using DigiWest multiplex protein profiling for a selection of 90 signalling proteins. Comparative analysis of the profiles identified a substantial change in the expression of 43 proteins. Differential PARP-1, AR, p53, Notch-3 and YB-1 protein levels were independently validated using Western Blotting. Pharmacological targeting of these proteins was associated with a mild but significant radiosensitisation effect at 4Gy. This study supports the clinical relevance of isogenic in vitro models of radioresistance and clarifies the molecular radiation response of prostate cancer cells.

P5681Improved electrical performance/stability of a novel active fixation coronary sinus lead compared to passive fixation leads: a multi-centre study

Background

A novel active fixation coronary sinus (CS) lead, Attain Stability, has been released in a bipolar and quadripolar configuration, with the hypothesis it will improve targeted lead positioning and stability independent of vessel anatomy.

Purpose

To compare implant procedure parameters and electrical performance/stability of a novel active fixation lead with passive fixation CS leads.

Methods

This was a retrospective study involving 6 major UK cardiac centres. Patients who received active leads were compared with passive lead recipients in a 1:2 ratio. The primary outcome was total lead displacements (combined macro/micro-displacements, defined as displacements requiring repositioning procedures, or an increase in threshold≥0.5 volts or pulse width≥0.5msec, or a change in pacing polarity). Multivariate analysis was performed to establish predictors of the primary outcome, assessing fixation mechanism (active or passive), number of poles (quad or bipolar), contributing hospital and follow-up duration.

Results

736 patients were included (241 with active leads, 495 with passive leads). There were no group differences in the baseline characteristics with respect to age, gender, EF, NYHA class, and co-morbidities, P>0.05 for all. The primary endpoint rate was 31% (74/241) in the active and 43% (213/495) in the passive fixation group (P=0.002). 6 patients in the active group and 14 in the passive group required CS lead repositioning procedures. The results of the multivariate analysis are presented in the Table. The use of active leads was associated with a significant reduction in lead displacements, odds ratio 0.62 (95% CI 0.43–0.9), P=0.012. There were differences in favour of passive compared with active leads in procedure duration, 120 [96–149] minutes vs 128 [105–155] minutes (P=0.011), and fluoroscopy time, 17 [11–26] minutes vs 18.5 [13–27] minutes (P=0.028). The median duration of follow up was similar (active vs passive): 31 [17–47] weeks vs 34 [16–71] weeks, (P=0.052).

Odds Ratio (95% Confidence Interval) P-value Active fixation CS lead 0.62 (0.43–0.9) 0.012 Quadripolar (rather than Bipolar) lead 1.26 (0.75–2.11) 0.376 Follow-up Duration (weeks) 1.005 (1.001–1.008) 0.025 Also included in the model: contributing hospital, which was significant.

Conclusion

In this large, multi-centre study, active fixation Attain Stability CS leads demonstrated superior electrical performance/stability compared with passive fixation leads, with minimal increases in implant procedure and fluoroscopy times.

Acknowledgement/Funding

None

Abstract P2-03-03: A multicenter clinical study of Xpert® breast cancer STRAT4 demonstrates high concordance with central lab ER, PgR, HER2, and Ki67 IHC and HER2 FISH tests in FFPE breast tumor tissues

The Xpert® Breast Cancer STRAT4 (STRAT4) is a CE-IVD marked, semi-quantitative, cartridge-based RT-qPCR assay for the detection of ESR1, PGR, ERBB2 (HER2), and MKi67 mRNAs from formalin fixed, paraffin embedded (FFPE) breast tumors. The assay is fast (&lt; 2 hrs), reproducible, robust, and easy to perform.

The aim of this multicenter clinical study was to assess the performance characteristics of the STRAT4 assay relative to central lab immunohistochemistry (IHC) for ER, PgR, HER2, and Ki67 and to fluorescence in situ hybridization (FISH) for HER2 gene amplification.

Methods: A total of 200 archived primary invasive breast cancer FFPE blocks were sourced from Indivumed for this study. From each block, twelve (12) adjacent tissue sections (4-µm thickness) on slides were prepared for pathological H&E confirmation to define tumor area, and for testing by STRAT4, IHC (ER, PgR, HER2,Ki67), and HER2 FISH. Standard STRAT4 lysate preparation using a single unstained slide per specimen and testing on N=84, N=68, and N=48 samples was performed at 3 independent sites, respectively (2 US and 1 EU). A single slide from each specimen was also processed using the recommended concentrated lysate procedure for STRAT4 testing at Cepheid. All IHC and FISH testing was performed by a central academic reference laboratory in the US. For a given sample, STRAT4 data generated using the standard lysate procedure was included for concordance analysis when all target gene test results were valid. In cases where the standard lysate preparation yielded indeterminate test results for any target, data from the concentrated lysate preparation was used for the data analysis. Receiver Operating Characteristic (ROC) analysis, overall percent agreement (OPA), positive percent agreement (PPA), and negative percent agreement (NPA) between STRAT4 and IHC (IHC/FISH for HER2) were determined for ESR1,PGR, ERBB2, and MKi67.

Results: Of the 200 samples tested by STRAT4, all samples generated valid results for ESR1 and ERBB2, 199 of 200 samples were valid for PGR, and 198 of 200 samples were valid for MKi67 using the standard or concentrated lysate preparation protocol. One sample failed to generate results for both ER and PgR IHC. Twelve samples failed to yield HER2 FISH results.

The STRAT4 success rate and results concordance with IHC were comparable across study sites. OPA between STRAT4 and IHC was 97% for ESR1, 88.9% for PGR, 93.3% for HER2 (92.4% for IHC and FISH), and 90.7% for MKi67 (excluding IHC 10-20% staining). Areas under the ROC curves were 0.9922 for ESR1, 0.9509 for PGR, 0.9958 for ERBB2, and 0.9395 for MKi67.

Conclusion: STRAT4 measurements for ESR1, PGR, ERBB2 and MKi67 mRNA expression are robust and highly concordant with IHC (IHC/FISH for HER2). The technical portion of the assay is easily performed in &lt; 2 hrs including hands-on time using standard FFPE tissue sections. Xpert STRAT4 offers local pathology labs an alternative to centralized, subjective IHC/FISH tests that require a higher level of expertise. Further investigations correlating STRAT4 markers directly with clinical outcomes in independent cohorts are in progress.

Citation Format: Wu NC, Wong E, Acca B, Birkmeier J, Tran L, Zhao S, Wong W, Chu VC, Ho K, Malek M, Lu C, Ge G, David K, Quigley NB, Beqaj SS, Davenport S, Weidler J, Bates M, Press M. A multicenter clinical study of Xpert® breast cancer STRAT4 demonstrates high concordance with central lab ER, PgR, HER2, and Ki67 IHC and HER2 FISH tests in FFPE breast tumor tissues [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-03-03.

Abstract P6-03-07: An automated DNA methylation assay (QM-MSP) for rapid breast cancer diagnosis in underdeveloped countries

BACKGROUND: Underdeveloped countries reported 882,900 new cases of breast cancer and 324,000 deaths in 2012, likely to be a gross underestimation according to recent reports. Often, mammography screening is not available, primary care services are limited, and pathology and treatment services are available only in the regional hospitals. Because of the lack of access to diagnostic and treatment services, it is estimated that more than 90% of patients with breast cancer never present for medical treatment. To address this situation, an accurate, easy-to-perform diagnostic test appropriate for use in remote clinics is desperately needed. Johns Hopkins (JH) and Cepheid partnered to translate a robust Quantitative Multiplex Methylation-Specific PCR (QM-MSP) assay to an automated, cartridge-based system that provides quantitative measures of DNA methylation within hours of fine needle aspiration or core biopsy of image-detected suspicious lesions.

METHODS: With a goal of discriminating malignant from benign breast disease with high sensitivity and specificity, we evaluated 24 breast cancer-specific DNA methylation markers (selected through comprehensive methylome analysis) in 119 invasive ductal carcinomas and 186 benign breast tissues. QM-MSP was performed on sections of formalin-fixed paraffin-embedded (FFPE) tissues to quantify DNA methylation. The dynamic range and performance of quantitative methylation detection was tested using a subset of 9 genes in the cartridge-based system.

RESULTS: QM-MSP was performed in a Training set consisting of 93 tissues [n=43 IDC, n=50 benign lesions (25 usual ductal hyperplasia, UDH, and 25 papilloma)] from the US. We selected 9 DNA markers significantly (p&lt;0.05) more methylated in malignant compared to benign lesions, which had low or no methylation. An independent Test set consisted of benign (n=26) and malignant (n=10) tissues (mostly Caucasian; JH Test Set). As a panel, the 9 markers were significantly more methylated in malignant than benign tissue (p&lt;0.001), revealing a sensitivity of 90% and specificity of 92%, using a laboratory cutoff of 9.5 CMI units (900 unit scale) based on receiver operator characteristic statistics (ROC; p&lt;0.0001, AUC=0.977). To determine if the markers characterized in the JH Test Set could perform as well in samples from a different geography, the panel was tested on 176 tissues from Wuhan, China (China Test Set). In this cohort (66 IDC and 110 benign tissues - 49 fibroadenoma, 19 benign cyst, 12 UDH, 30 papilloma), sensitivity was 89% and specificity was 89% for detection of breast cancer with ROC AUC=0.945. An advanced version of the cartridge with up to 12 methylated DNA markers is under development, thus far showing robust signals in cancer and low background in benign tissues. Current work at JH is focused on optimizing the technical performance of the cartridge.

CONCLUSIONS: We identified a panel of methylated DNA markers that discriminate malignant from benign breast lesions and built a prototype automated cartridge-based assay with promising sensitivity and specificity for breast cancer. Such an assay has the potential to aid in specimen triage in the pathology lab and provide fast, low cost and accurate diagnosis of breast cancer in LMIC settings.

Citation Format: Fackler MJ, Downs BM, Mercado-Rodriguez C, Cimino-Mathews A, Chen C, Yuan J, Cope LM, Kohlway A, Kocmond K, Lai E, Weidler J, Visvanathan K, Umbricht CB, Harvey S, Wolff AC, Bates M, Sukumar S. An automated DNA methylation assay (QM-MSP) for rapid breast cancer diagnosis in underdeveloped countries [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-03-07.

Abstract P2-03-02: Macrodissection prior to closed system RT-qPCR is not necessary for estrogen receptor and HER2 concordance with IHC/FISH in breast cancer

Background: An on-demand, closed system RT-qPCR (the GeneXpert system, Cepheid, Sunnyvale, CA) has the potential to provide biomarker information in low resourced settings. The system consists of an inexpensive, single-use, disposable, macrofluidic cartridge and an instrument that automates RT-qPCR. Here we use it with a research use only cartridge (STRAT4) that measures the mRNA expression levels of ESR1, PGR, ERBB2, and MKi67 using a single 5uM thick FFPE tissue section from an excisional or core biopsy specimen containing invasive carcinoma of the breast. The assay, results are expressed as a delta cycle threshold (dCt) value, defined as the Ct of a control gene (CYFIP1) minus the Ct of the target gene (ESR1, PGR, ERBB2, or MKi67). We determine whether the dCt result for each marker is equivalent using the entire non-macrodissected section (non m-d) to the dCt results obtained following tumor macro-dissection (m-d) to eliminate non-tumor elements from the assay.

Methods: We evaluated the impact of m-d versus non m-d using STRAT4 on a cohort of 62 formalin-fixed paraffin-embedded (FFPE) tumor core needle biopsy specimens with a range of HER2 expression determined by clinical immunohistochemistry and fluorescence in situ hybridization (IHC/FISH). Concordance (sensitivity and specificity) of the STRAT4 ESR1 and HER2 mRNA versus ER and HER2 IHC/FISH measurements were also assessed.

Results: We observed excellent agreement of the resulting dCt between the paired samples, m-d versus non m-d, for ESR1 (R2=0.92), PGR (R2=0.90), ERBB2 (R2=0.94) and MKi67 (R2=0.90). No significant difference (P value &gt; 0.99) was observed when we compared the dCt between the paired samples m-d versus non m-d. In addition, using the predefined STRAT4 dCt cutoff for ESR and ERBB2 positivity, we found a significant concordance between RT-qPCR and IHC/FISH for ESR-positivity for the paired samples, m-d (P value &lt; 0.001; sensitivity = 0.98; specificity = 1; PPV = 1; NPV = 0.95) versus non m-d (P value &lt; 0.001; sensitivity = 0.98; specificity = 1; PPV = 1; NPV = 0.95) and HER2-positivity for the paired samples, m-d (P value &lt; 0.001; sensitivity = 0.85; specificity = 0.98; PPV = 0.92; NPV = 0.96) versus non m-d (P value &lt; 0.001; sensitivity = 0.71; specificity = 0.98; PPV = 0.90; NPV = 0.92), respectively.

Conclusion: These data suggest that mRNA for ESR and ERBB2 is sufficiently low in surrounding tissues that m-d of whole sections is not required for accurate assessment of key breast cancer mRNA markers in a closed system RT-qPCR assay. The simplicity of the assay workflow may be particularly valuable in low resourced settings where routine access to pathology expertise and to high quality IHC/FISH is challenging.

Citation Format: Gupta S, Carvajal-Hausdorf DE, Wasserman BE, Ho K, Weidler J, Wong W, Rhees B, Bates M, Rimm DL. Macrodissection prior to closed system RT-qPCR is not necessary for estrogen receptor and HER2 concordance with IHC/FISH in breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-03-02.

Abstract P1-03-03: High concordance of ER, PR, HER2 and Ki67 by central IHC and FISH with mRNA measurements by GeneXpert® breast cancer stratifier assay

Current methods for the assessment of ER, PR, Her2, and Ki67 using FFPE tissues are hard to standardize and difficult to perform in Low and Middle Income Countries (LMIC). The GeneXpert® breast cancer stratifier assay (RUO) (BC Strat) is a cartridge-based, RT-qPCR assay of ESR1, PGR, ERBB2, and MKi67 mRNAs using FFPE specimens. The assay is fast (&lt;2 hours, including &lt;10 minutes of hands-on time) and easy to perform.

The aims of this study were: 1) to evaluate the concordance of BC Strat using different IHC antibodies and scoring methods in a preliminary dataset (Part I); and 2) to assess concordance between BC Strat and high quality standard methods in an expanded dataset (Part II).

Methods

Part I: IHC Antibody Variability

To assess BC Strat concordance with various IHC antibodies, 155 invasive ductal carcinoma blocks were sourced from 3 sites. Twenty-four adjacent slide sections from each block were prepared and shipped to different labs for BC Strat analysis(Cepheid) or IHC and FISH testing. Table 1 summarizes the IHC antibodies and scoring methods used in each reference lab.

Table 1:IHC antibodies and scoring methods used in reference labs Antibody for IHClabIHC scoringERSP1MPLNAutomated (Aperio)ER6F11Path IncAutomated (Aperio)ER6F11USCManualPRIE2MPLNAutomated (Aperio)PR16Path IncAutomated (Aperio)PRPGR636USCManualHer2*4B5MPLNAutomated (Aperio)Her2*HercepTestUSCManualKi6730-9MPLNAutomated (Aperio)Ki67MIB1Path IncAutomated (Aperio)Ki67MIB1USCManual*HER2 FISH (all with PathVysion kit) was performed at USC

Part II: Concordance Study

522 invasive ductal carcinoma FFPE samples were sourced from 5 sites. All BC Strat analysis was performed at Cepheid and all IHC and FISH was performed in the Press laboratory at USC. Overall percent agreement (OPA), positive percent agreement (PPA), and negative percent agreement (NPA) between BC Strat and IHC were determined.

Results

Part I: IHC Antibody Variability

Table 2 summarizes the OPA for BC Strat analysis and IHC performed with different IHC antibodies and scoring methods. Slightly better concordance for ER and PR was observed between the BC Strat and the IHC methods performed at USC. Discordant IHC results were also observed among the reference labs' standard methodologies.

Table 2: Overall Percent Agreement between IHC and BC Strat Reference LabOPA with BC StratERMPLN92%ERPath Inc96%ERUSC98%PRMPLN84%PRPath Inc83%PRUSC87%Her2*MPLN*93%Her2*USC*91%Ki67MPLN75%Ki67Path Inc67%Ki67USC81%*for IHC 2+(equivocal), FISH HER2/CEP17 ratio was examined

Part II: Concordance Study

Of the 522 samples tested, 499 (96%) yielded valid results for both BC Strat and IHC (IHC and FISH for Her2). OPA between BC Strat and IHC was 98% for ESR1, 91% for PGR, 93% for ERBB2 (IHC and FISH, 97% for Her2 IHC excluding IHC2+), and 81% for MKi67.

Conclusion

BC Strat assay measurements for ESR1, PGR, ERBB2 and MKi67 mRNA expression in FFPE breast tumor tissues are highly concordant with IHC and FISH performed by high quality reference labs. Further investigations using clinical outcomes from independent studies including prospective-retrospective clinical trials are in progress.

Citation Format: Wu NC, Wong W, Ho KE, Chu VC, Rizo A, Davonport S, Kelly D, Makar R, Jassem J, Duchnowska R, Biernat W, Radecka B, Fujita T, Klein JL, Stonecypher M, Ohta S, Juhl H, Weidler JM, Bates M, Press MF. High concordance of ER, PR, HER2 and Ki67 by central IHC and FISH with mRNA measurements by GeneXpert® breast cancer stratifier assay [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 P1-03-03.

Abstract P1-03-11: Analytical validation for the RT-qPCR based multiplex mRNA measurements of ER, PgR, HER2, and Ki67 from FFPE tumor tissue using the GeneXpert breast cancer stratifier assay

BACKGROUND: Accurate assessment of ER, PgR, HER2 and Ki67 status is crucial for breast cancer therapy and patient management. Immunohistochemistry (IHC) assays have been standard diagnostic tools but they are complex and time-consuming to perform and may not be readily available in decentralized laboratories, particularly in low-to-middle income countries. Molecular diagnostics can be a sensitive and accurate alternative to the traditional IHC, and the GeneXpert Breast Cancer Stratifier assay RUO (BC Strat), a single use cartridge-based assay performed on the broadly distributed GeneXpert® Instrument (GX) platform, streamlines a technically demanding RT-qPCR process to provide easy, robust, and reproducible ESR1, PGR, ERBB2, and MKi67 mRNA measurements from a 4 µm thick, formalin-fixed paraffin embedded (FFPE) breast tumor section in less than 2 hours.

METHODS: Analytical validation of the BC Strat assay included studies of Linearity/Dynamic Range, Analytical Sensitivity (Minimum Assay Input), Specificity (Potential Interfering Substances), Carryover Contaminations, and Kit and Specimen Slide Stabilities. Both in-vitro RNA transcript (IVT) and/or clinical breast cancer tissues were used as sample input materials. Assay results for each analyte were generated from cycle threshold (Ct) values, and final positive/negative test results for each target were also reported as delta Ct values, where dCt = Ct [CYFIP1 Reference] – Ct [Target], using dCt cutoffs previously derived from a clinical sample cohort.

RESULTS: The BC Strat assay demonstrated ≥3 log Linear Dynamic Range covering 5-7 logs sample input for all 4 Target dCts with R2≥0.95 independently. The assay currently requires minimal sample input equivalent to CYFIP1 Ct≤35 (Ct=33.5 ±1.5Ct SD) from 20 replicates of 5-level serial sample dilutions using two independent assay lot materials. It is acceptably robust against non-tumor tissues, DCIS, necrotic and/or hemorrhagic cells, lymphocytes, and genomic DNA contaminants. No carryover contamination from the same GeneXpert module was observed over 20 repeat tests during 9 consecutive days. Current real-time data supports assay stability at 5, 30, 37, 45 and 50°C for at least 3 months with minimal performance impact. Sectioned FFPE breast tumor tissues generated consistent dCt results when stored at 4°C and 30°C for up to 1 month before BC Strat assay testing.

CONCLUSIONS: The analytical validations of the BC Strat assay demonstrate an easy and robust mRNA detection with high sensitivity, specificity, reproducibility, and stability in order to aid medical pathologists and clinicians to more rapidly and objectively determine ESR1, PGR, ERBB2, and MKi67 mRNA status in breast cancer. Although stability studies out to 37 months are ongoing, current data suggest the assay is stable for at least 3 months over a wide range of temperatures. The GeneXpert Breast Cancer Stratifier assay potentially offers a rapid, standardized, and cost-effective solution to streamlining complex molecular diagnostics available for use in local pathology laboratories worldwide.

Citation Format: Chu VC, Wu N, Ho KE, Rizo A, Malek M, Weidler JM, Bates M, Wong W. Analytical validation for the RT-qPCR based multiplex mRNA measurements of ER, PgR, HER2, and Ki67 from FFPE tumor tissue using the GeneXpert breast cancer stratifier assay [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 P1-03-11.

Abstract P1-03-09: Highly reproducible decentralized gene expression analysis of ESR1, PGR, ERBB2 and MKi67 on an automated, standardized molecular diagnostics platform, GeneXpert

Background: Accurate assessment of ER, PgR, HER2, and Ki67 status using FFPE samples from patients with breast cancer is critical for appropriate patient management, yet immunohistochemistry (IHC), the most common method of assessing these markers, suffers from inherent variability due to pre-analytical/analytical factors and subjective interpretation by pathologists. Here we describe the GeneXpert (GX) Breast Cancer Stratifier RUO Assay (BC Strat), a real time quantitative PCR assay (RT-qPCR) kit which exhibits robust, highly reproducible mRNA measures of ESR1, PGR, ERBB2 (HER2) and MKi67.

The aims of this study were: 1) To assess the impact of variability contributed by pathologist-to-pathologist differences in the selection of the tumor area to be assayed, inter-laboratory assay performance, and macrodissection (MAC) vs. no macrodissection (nonMAC) on decentralized BC Strat results; and 2) to assess preliminary concordance of BC Strat with central IHC and FISH results.

Materials & Methods: The GX BC Strat is a cartridge-based RT-qPCR assay performed on the GeneXpert® Instrument (Cepheid) that automates RNA purification, RT-qPCR amplification and detection of mRNA of target genes (ESR1, PGR, ERBB2, and MKi67) and a control gene (CYFIP1) after sample preparation. Results are reported as delta cycle threshold (dCt) measurements (CYFIP1 Ct - target gene Ct) in less than 2 hrs.

Thirty-two invasive ductal carcinoma FFPE blocks were sourced based on varying levels of ER, PgR, HER2, and Ki67 expression and % tumor cell content/tumor area. Adjacent sections from each block were prepared as slides and sent to 3 external GX testing sites and a reference lab. Each site used its own pathologists/technicians to determine the % tumor cell content/tumor area, perform MAC or nonMAC, prepare lysates, and perform GX testing. Reference IHC/FISH was performed by Geneuity/MPLN (Maryville, TN, USA). Site-to-site concordance in GX results for MAC or nonMAC samples using pre-defined assay cutoffs per marker were analyzed, as were % tumor cell content/tumor area assessments between pathologists.

Results: BC Strat testing of 32 FFPE breast cancer samples with MAC demonstrated excellent GX site-to-site concordance in positive/negative status calls for ESR1 (100%), PGR (100%), ERBB2 (97%), and MKi67 (97%). In most cases, MAC vs. nonMAC had minimal impact on final positive/negative calls for GX, resulting in high overall concordance for MAC vs. nonMAC for ESR1 (91%), PGR (99%), ERBB2 (99%), and MKi67 (95%). The assay also demonstrated a strong overall concordance with IHC for ESR1 (97%), PGR (81%), ERBB2 (98%, IHC/FISH), and MKi67 (89%).

Conclusion: Decentralized performance of the GX BC Strat Assay is feasible and minimally affected by differences in tumor area selection and MAC techniques across tumors with a range of sizes, invasive tumor cell contents, and expression levels of ER, PgR, HER2, and Ki67. GX BC Strat dCt results across sites are highly reproducible and show good concordance of results with central lab IHC and HER2 FISH results. These results suggest standardized, decentralized testing of ESR1, PGR, ERBB2 and MKi67 by the GX BC Strat in local pathology labs is feasible.

Citation Format: Wong W, Ho KE, Wu N, Chu VC, Lalli P, Longshore JW, Klein J, Stonecypher M, Lykke C, Sherwood T, Davenport S, Weidler J, Bates M, Press MF. Highly reproducible decentralized gene expression analysis of ESR1, PGR, ERBB2 and MKi67 on an automated, standardized molecular diagnostics platform, GeneXpert [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 P1-03-09.

Abstract P1-03-07: High concordance of a closed system, near point of care, RT-qPCR breast cancer assay for HER2 (ERBB2) mRNA compared to both IHC/FISH and quantitative immunofluorescence

Background

Reliable assessment of HER2 receptor status in breast cancer by either IHC or FISH does not unequivocally define receptor expression, due to their semi-quantitative nature, and as many as 10-15% of cases fall into the ASCO/CAP “equivocal” category. Historically, RNA measurements by PCR, including using several commercially available platforms, have been tested, but have not gained broad acceptance for assessment of HER2. However, RNA measurement, as a continuous value, has potential for use for adjudication of the equivocal category. In the current study, we used a real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) assay (GeneXpert® Breast Cancer Stratifier RUO Assay, Cepheid, Sunnyvale, CA, USA) for ERBB2 (HER2) mRNA on the GeneXpert® (GX) platform (Cepheid), which utilizes a closed-system, single-use cartridge, automated system. The RT-qPCR results from GX were then compared with results from clinical HER2 IHC/FISH assays following ASCO/CAP 2013 HER2 testing guidelines (Wolff et al JCO 2013) and quantitative immunofluorescence (QIF).

Methods

Multiple cores (1mm in diameter) were retrospectively collected from 80 formalin-fixed paraffin-embedded (FFPE) tissue blocks with invasive breast cancer seen by Yale Pathology Labs between 1998 and 2011. Tissue cores were processed as lysates for testing at Yale in the automated GX assay. Briefly, gene-specific reverse transcription was performed, followed by RT-qPCR (TaqMan) and ERBB2 mRNA results were expressed as the difference in cycle threshold values (delta Ct) between the endogenous control transcript (CYFIP1) and the ERBB2 mRNA transcript. Results from IHC and FISH were extracted from the pathology reports for the Yale CLIA lab and QIF for each case was measured as previously described (Carvajal et al, JNCI 2015).

Results

Quality control testing showed that the GX platform shows no case to case cross contamination on material from routine histology practices. Concordance between RT-qPCR and IHC/FISH was 91.25% (sensitivity = 0.87; specificity = 0.94; PPV = 0.89; NPV = 0.92) using a pre-defined delta Ct cut-off (dCt ≥ -1) for HER2 (+) based on prior concordance studies with HER2 IHC/FISH. Concordance between RT-qPCR and QIF was 99% (sensitivity = 0.97; specificity = 1.0; PPV = 1.0; NPV = 0.98) using dCt ≥ -1 and the pre-defined cut-point for positivity by QIF.

Conclusions

The GX closed system RT-qPCR assay shows greater than 90% concordance with the ASCO/CAP 2013 HER2 IHC/FISH scoring. Additionally, the GX RT-qPCR assay is highly concordant (99%) with the continuous variable HER2 QIF assay, and may better reflect the true continuum of HER2 receptor status in invasive breast cancer. These initial results suggest that rapid, closed system molecular assays may have future value for the adjudication of the ASCO/CAP HER2 equivocal category. This pilot study did not include ASCO/CAP 2013 “equivocal” cases, but that effort is underway.

Citation Format: Wasserman B, Carvajal-Hausdorf D, Ho K, Wong W, Wu N, Chu VC, Lai EW, Weidler JM, Bates M, Neumenister V, Rimm DL. High concordance of a closed system, near point of care, RT-qPCR breast cancer assay for HER2 (ERBB2) mRNA compared to both IHC/FISH and quantitative immunofluorescence [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 P1-03-07.

Triage of LSIL/ASC-US with p16/Ki-67 dual staining and human papillomavirus testing: a 2-year prospective study

OBJECTIVE

To investigate human papillomavirus (HPV) DNA testing and p16/Ki-67 staining for detecting cervical intraepithelial grade 2 or worse (CIN2+) and CIN3 in women referred to colposcopy with minor abnormal cervical cytology low-grade squamous intraepithelial lesions (LSIL) and atypical squamous cells of undermined significance (ASC-US). The clinical performance of both tests was evaluated as stand-alone tests and combined, for detection CIN2+ and CIN3 over 2 years.

METHODS

ThinPrep(®) liquid-based cytology (LBC) specimens were collected from 1349 women with repeat LSIL or ASC-US. HPV DNA was performed using Hybrid Capture. Where adequate material remained (n = 471), p16/Ki-67 overexpression was assessed. Clinical performance for detection of histologically diagnosed CIN2+ and CIN3 was calculated.

RESULTS

Approximately 62.2% of the population were positive for HPV DNA, and 30.4% were positive for p16/Ki-67. p16/Ki-67 showed no significant difference in positivity between LSIL and ASC-US referrals (34.3% versus 28.6%; P = 0.189). Women under 30 years had a higher rate of p16/Ki-67 compared to those over 30 years (36.0% versus 26.6%; P = 0.029). Overall HPV DNA testing produced a high sensitivity for detection of CIN3 of 95.8% compared to 79.2% for p16/Ki-67. In contrast, p16/Ki-67 expression offered a higher specificity, 75.2% versus 40.4% for detection of CIN3. Combining p16/Ki-67 with HPV DNA improved the accuracy in distinguishing between CIN3 and <CIN3. The absolute risk of CIN3 increased from 15.6% in women who were HPV DNA positive to 27% in women positive for HPV DNA and p16/Ki-67. Those negative for HPV DNA and p16/Ki-67 had a low risk of 1.2% of CIN3.

CONCLUSION

The addition of p16/Ki-67 to HPV DNA testing leads to a more accurate stratification of CIN in women presenting with minor cytological abnormalities.

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&lt;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.

Inflammatory and bone turnover markers in a cross-sectional and prospective study of acute Charcot osteoarthropathy

AIMS

To assess markers of inflammation and bone turnover at presentation and at resolution of Charcot osteoarthropathy.

METHODS

We measured serum inflammatory and bone turnover markers in a cross-sectional study of 35 people with Charcot osteoarthropathy, together with 34 people with diabetes and 12 people without diabetes. In addition, a prospective study of the subjects with Charcot osteoarthropathy was conducted until clinical resolution.

RESULTS

At presentation, C-reactive protein (P = 0.007), tumour necrosis factor-α (P = 0.010) and interleukin-6 (P = 0.002), but not interleukin-1β, (P = 0.254) were significantly higher in people with Charcot osteoarthropathy than in people with and without diabetes. Serum C-terminal telopeptide (P = 0.004), bone alkaline phosphatase (P = 0.006) and osteoprotegerin (P < 0.001), but not tartrate-resistant acid phosphatase (P = 0.126) and soluble receptor activator of nuclear factor-κβ ligand (P = 0.915), were significantly higher in people with Charcot osteoarthropathy than in people with and without diabetes. At follow-up it was found that tumour necrosis factor-α (P = 0.012) and interleukin-6 (P = 0.003), but not C-reactive protein (P = 0.101), interleukin-1β (P = 0.457), C-terminal telopeptide (P = 0.743), bone alkaline phosphatase (P = 0.193), tartrate-resistant acid phosphatase (P = 0.856), osteoprotegerin (P = 0.372) or soluble receptor activator of nuclear factor-kβ ligand (P = 0.889), had significantly decreased between presentation and the 3 months of casting therapy time point, and all analytes remained unchanged from 3 months of casting therapy until resolution. In people with Charcot osteoarthropathy, there was a positive correlation between interleukin-6 and C-terminal telopeptide (P = 0.028) and tumour necrosis factor-α and C-terminal telopeptide (P = 0.013) only at presentation.

CONCLUSIONS

At the onset of acute Charcot foot, serum concentrations of tumour necrosis factor-α and interleukin-6 were elevated; however, there was a significant reduction in these markers at resolution and these markers may be useful in the assessment of disease activity.

Human cytomegalovirus infant infection adversely affects growth and development in maternally HIV-exposed and unexposed infants in Zambia

BACKGROUND

Human immunodeficiency virus (HIV) and human cytomegalovirus (HCMV) coinfections have been shown to increase infant morbidity, mortality, and AIDS progression. In HIV-endemic regions, maternal HIV-exposed but HIV-uninfected infants, which is the majority of children affected by HIV, also show poor growth and increased morbidity. Although nutrition has been examined, the effects of HCMV infection have not been evaluated. We studied the effects of HCMV infection on the growth, development, and health of maternally HIV-exposed and unexposed infants in Zambia.

METHODS

Infants were examined in a cohort recruited to a trial of micronutrient-fortified complementary foods. HIV-infected mothers and infants had received perinatal antiretroviral therapy to prevent mother-to-child HIV transmission. Growth, development, and morbidity were analyzed by linear regression analyses in relation to maternal HIV exposure and HCMV infection, as screened by sera DNA for viremia at 6 months of age and by antibody for infection at 18 months.

RESULTS

All HCMV-seropositive infants had decreased length-for-age by 18 months compared with seronegative infants (standard deviation [z]-score difference: -0.44 [95% confidence interval {CI}, -.72 to -.17]; P = .002). In HIV-exposed infants, those who were HCMV positive compared with those who were negative, also had reduced head size (mean z-score difference: -0.72 [95% CI, -1.23 to -.22]; P = .01) and lower psychomotor development (Bayley test score difference: -4.1 [95% CI, -7.8 to -.5]; P = .03). HIV-exposed, HCMV-viremic infants were more commonly referred for hospital treatment than HCMV-negative infants. The effects of HCMV were unaffected by micronutrient fortification.

CONCLUSION

HCMV affects child growth, development, and morbidity of African infants, particularly in those maternally exposed to HIV. HCMV is therefore a risk factor for child health in this region.

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.

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.

Multiple Subtypes of HER-2/Neu-Positive Metastatic Breast Cancer

Background: Using IHC or FISH to select patients for trastuzumab-based therapy, only half of HER2-positive patients show evidence of response. In vitro data implicate HER2:HER3 heterodimers and p95HER2 (p95), the truncated 95-kilodalton C-terminal fragment of HER-2 lacking the trastuzumab binding site, as mediators of resistance to trastuzumab at the receptor level. We have previously reported that central FISH-positive patients with low HER2 protein expression by VeraTag had significantly reduced response to trastuzumab compared to patients who had FISH-positive tumors with high HER2 protein expression (Lipton, SABCS 2008). Adding quantitative measurements of HER3 and p95, we offer evidence for the existence of multiple sub-types of HER2-positive tumors that respond differently to trastuzumab.Methods: Using the VeraTag assay, quantitative protein measurements of HER2, HER3, and p95 were made in FFPE specimens from a cohort of patients with metastatic breast cancer (MBC) and correlated with time to progression (TTP) and overall survival (OS) following treatment with first-line trastuzumab using Kaplan-Meier (KM) and Cox proportional hazards regression analyses.Results: Measurements of HER2 (H2T), HER3 (H3T) and p95 were made in FFPE tumor samples from 95 patients treated with first-line trastuzumab for metastatic breast cancer. Within the group that overexpressed HER2 by the VeraTag Assay (n=60), a group with highly overexpressed HER2 (n=15) had shorter TTP and OS than those that had moderate HER2 overexpression (median TTP 4.6 vs. 12 mos, HR=2.1; p=0.011; median OS 29 vs. 40 mos, HR=2.0; p=0.047). Within the subgroup with moderate H2T overexpression (n=45), bivariate Cox analyses demonstrated that p95 and H3T were independent predictors of TTP (p95 HR=2.1; p=0.031; H3T HR=3.5; p=0.0037). For OS, p95 was significant and H3T showed a strong trend (p95 HR=2.5; p=0.025, H3T HR=2.2; p=0.089). Univariate KM analysis with the p95+ and H3T+ groups combined, gives the results in the table below. These data suggest that HER2-positive breast cancer patients can be classified into at least 4 sub-groups with different outcomes following trastuzumab treatment.Conclusions: These data suggest the existence of multiple subgroups of HER2-positive patients expressing varying HER2, p95, and HER3 levels that experience different clinical outcomes following treatment with trastuzumab. Furthermore, the association of HER3 and p95 overexpression with poor response to trastuzumab in otherwise HER2-positive tumors suggests possible treatment approaches with combinations of targeted therapies.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2030.

Breast Cancer Patients with Very High Tumor HER2 Expression Levels Might Not Benefit from Treatment with Trastzumab Plus Chemotherapy: A Retrospective Exploratory Analysis of the FinHer Trial

Background: FinHer (NEJM 2006) is one of the several prospective randomized clinical trials that show a clinical benefit from trastuzumab added to adjuvant chemotherapy. We have previously reported that patients with metastatic breast cancer who had very high levels of HER2 protein expression as measured by the HERmark assay and who were treated with trastuzumab had similar time-to-progression (TTP) compared to a group of patients who had FISH-negative and HER2 normal cancer suggesting reduced efficacy of trastuzumab when tumor HER2 content is very high (Sperinde, ASCO 2009). Here we investigate the relationship between clinical benefit from trastuzumab and quantitative HER2 protein expression (H2T) as determined by the HERmark assay.Methods: H2T was quantitated by the HERmark assay in 899 formalin-fixed paraffin-embedded specimens from patients enrolled in the FinHer trial; 196 of the samples were HER2-positive by chromogenic in situ hybridization (CISH). Focusing on the HER2-positive patients who were randomized to trastuzumab treatment or control, Cox proportional hazards analyses, sub-population treatment effect pattern plots (STEPP analyses), positional scanning analyses, and Kaplan-Meier analyses were used to identify sub-populations of HER2 over-expressing patients who experienced different clinical outcomes on trastuzumab.Results: Using time to distant recurrence (TDR) and overall survival (OS) as endpoints, Cox proportional hazards analyses treating H2T as a continuous variable failed to show a relationship between HER2 expression levels and clinical benefit from trastuzumab (HR=1, p=ns for both). STEPP analyses were performed to look for non-linear relationships between H2T and clinical outcome. At the highest levels of H2T, the hazard ratio comparing trastuzumab treatment to control approached and exceeded 1. Positional scanning analyses were conducted to identify the optimal cutoff discriminating the very high H2T group. Patients with very high H2T values (&gt;= 125.9) did not benefit from trastuzumab plus chemotherapy treatment relative to controls (HR=1.23, p=0.75 for TDR, HR=1.05, p=0.95 for OS), while those with H2T values &lt;125.9 did (HR=0.52, p=0.05 for TDR, HR=0.48, p=0.1 for OS). The very high H2T group represented 13% of the HER2-positive population compared with 16% in the prior study from Sperinde et al.Discussion: In this exploratory analysis of a prospectively randomized controlled trial of trastuzumab in the adjuvant setting, the 13% of patients with the highest H2T values showed no evidence of clinical benefit from trastuzumab. Potential explanations include insufficient trastuzumab dose, steric hindrance preventing access of trastuzumab to its epitope target under conditions of HER2 over-crowding, or the existence of trastuzumab-resistant forms of HER2 at the highest levels of over-expression (e.g. p95/HER2, HER2:HER3 heterodimers). Although these results are in agreement with prior observations from the metastatic setting, they need to be confirmed in larger randomized trials of trastuzumab in early breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5083.

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.

Quantitative measurement of HER3 total protein (H3T) and association with clinical outcome in HER2-positive metastatic breast cancer patients treated with trastuzumab

1021

Background: The heterodimerization of HER3, with HER2 and the subsequent activation of the AKT pathway, has been implicated in both regulation of tumor cell growth and in resistance to HER2 targeted therapies such as trastuzumab. Currently available methods of measuring H3T in formalin-fixed, paraffin-embedded (FFPE) samples are insufficiently sensitive or specific; thus the impact of quantitative measurement of H3T expression on clinical response to trastuzumab has not been evaluated. Methods: We have developed a highly quantitative, accurate, precise, sensitive, and reproducible H3T assay in FFPE samples based on the VeraTag technology platform. Consequently, the H3T assay displays ∼5-fold greater sensitivity than conventional IHC measurements. Additionally, the rank order and accuracy of the H3T measurements were preserved over a wide dynamic range in well-characterized cell line panels. Intra- and inter-assay reproducibility measurements demonstrated 7–11 %CV and 8–16 % CV, respectively. Results: Quantitative levels of HER2 total protein (H2T) and H3T expression were determined by the VeraTag technology in 81 tumors from patients with trastuzumab-treated metastatic breast cancer. A previously reported H2T cutoff was used to sub-divide the patients into HER2-normal (N = 26, median TTP = 4.1 mos) and HER2-overexpressing (N = 55, median TTP = 11.1 mos, HR = 0.43, p = 0.0002) groups. In the HER2-overexpressing group, high H3T expression, as defined by a positional scanning cutoff analysis, predicted shorter median time to progression (N = 25, median TTP = 6.1 mos) compared with low H3T expression (N = 30, median TTP = 13.1 mos, HR = 2.7, p = 0.0002). Univariate Cox proportional hazards analyses examining the HER2-overexpressing subgroup identified H3T (high vs. low) as the most significant predictor of TTP (HR = 2.98, p = 0.0004). Conclusions: These results demonstrate that the accurate and sensitive measurement of H3T in a cohort of patients with HER-2 positive breast cancer predicts TTP in response to trastuzumab and could indicate a population of patients with worse outcome requiring additional therapeutic intervention.

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

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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.

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

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Background: Many HER2-positive patients with metastatic breast cancer (MBC) fail to respond to trastuzumab. We previously reported that precise quantitation of HER2 expression (H2T) by the HERmark assay identified a sub-population of IHC 3+, FISH(+) (positive) patients with low H2T levels that responded poorly to trastuzumab (Lipton, San Antonio Breast Cancer Symposium 2008, abs #32). Here we identify a sub-population of FISH(+) patients with very high H2T levels, that experience clinical outcomes that are indistinguishable from those of FISH(-) (negative) patients with low H2T levels. Methods: The HERmark assay was used to measure H2T in formalin-fixed, paraffin-embedded (FFPE) primary breast tumor specimens from 99 women treated with trastuzumab for MBC. Specimens were also tested by central FISH. A sub-population treatment effect pattern plot (STEPP) was generated to examine the progression-free survival (PFS) rate at 12 months after treatment with trastuzumab across the distribution of H2T. Kaplan-Meier (KM) analyses were performed comparing the PFS of FISH(-), H2T low (log10H2T < 1.25) patients with those of FISH(+), H2T high (log10H2T ≥ 1.95) and FISH(+), H2T intermediate (1.25 < log10H2T < 1.95) groups. Cutoffs were identified by lowest p-value in a positional scanning analysis. Results: The PFS rate improved gradually with increasing H2T in STEPP analyses. At the highest levels of H2T, an abrupt decrease in the PFS rate was observed, consistent with a reduction in susceptibility to trastuzumab. KM analyses demonstrated that patients who were FISH(+), H2T intermediate had a significantly longer PFS than patients who were FISH(-), H2T low (median PFS 12.6 vs. 4.5 mos; HR = 0.34; p < 0.0001). Patients that were FISH(+), H2T high experienced a PFS that was no better than patients that were FISH(-), H2T low (median PFS 4.6 vs. 4.5 mos; HR = 0.87; p = 0.68). Conclusions: Precise quantitation of HER2 expression levels allows the identification of multiple sub-populations of HER2(+) patients that have different clinical outcomes on trastuzumab. MBC patients with very high levels of H2T could represent a sub-group with de novo resistance to trastuzumab who may benefit from combined therapy.

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