HER2 status assessment in breast cancer. Marc van de Vijver Academic Medical Centre (AMC), Amsterdam

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1 HER2 status assessment in breast cancer Marc van de Vijver Academic Medical Centre (AMC), Amsterdam 13e Bossche Mamma Congres 17 th June 2015

2 Modern cancer therapies are based on sophisticated molecular approaches Class Agent Indication Target Monoclonal antibodies Avastin mcrc, mbc, NSCLC, mrcc VEGF Herceptin Breast cancer, mgc HER2 Cetuximab Panitumumab mcrc*, SCC mcrc* EGFR TKI Tarceva NSCLC, pancreatic cancer Sorafenib HCC, RCC Sunitinib mrcc, GIST Multiple receptor tyrosine kinases Oestrogen receptor blockers Tamoxifen Breast cancer ER The ultimate goal is to obtain one or more biomarkers for each agent that can predict response to therapy *Tumours expressing wild-type KRAS GIST = gastrointestinal stromal tumour; mgc = metastatic gastric cancer SCC = squamous cell carcinoma of the head and neck

3 HER2: is also known as neu or c-erbb-2 the HER2 gene encodes the HER2 protein, which is a growth factor receptor located in the membrane of the cell

4 Transmembrane structure of HER2 monomer Extracellular domain (632 amino acids) Ligand-binding site Plasma membrane Cytoplasm Intracellular domain (22 amino acids) Intracellular domain (580 amino acids) Tyrosine kinase activity

5 HER2 gene amplification HER2 mrna over-replication + selection of cells with growth advantage HER2 protein normal amount HER2 mrna HER2 protein elevated amount

6 Significance of HER2 status 15% of breast carcinomas are HER2 positive Assessment of HER2 status is essential to determine patient eligibility for HER2 targeted therapy

7 Normal HER2 expression

8 HER2 amplification leads to HER2 overexpression

9 HER2 overexpression leads to tumour proliferation

10 Binding of Herceptin to HER2

11 Methods for HER2 testing Immunohistochemistry In situ hybridization (FISH, CISH, SISH)

12 HER2 testing algorithm Patient Tumour Sample IHC FISH FISH Herceptin Therapy Herceptin Therapy - + Herceptin Therapy Bilous et al., Mod Pathol. 16, 2003; Review on national testing guidelines

13 IHC scoring: semi-quantitative interpretation of HER2 expression 0 (negative) 1+ (negative) 2+ (equivocal) 3+ (positive)

14 FISH scoring: quantitative analysis of HER2 amplification FISH negative (no amplification) Ratio of HER2 gene (orange) to CEP17 (green) signals is <2.0 FISH positive Ratio of orange to green signals is >2.2 FISH, fluorescence in situ hybridisation Images courtesy of W Hanna using PathVysion

15 SISH scoring: quantitative analysis of HER2 amplification SISH negative SISH positive

16 Sources of variation in HER2 testing Reporting elements Scoring system Time to slicing and fixation Method of tissue processing Time of fixation Interpretation criteria Post-analytic Pre-analytic Type of fixation Use of image analysis HER2-testing variation Assay validation Assay conditions Controls Analytic Laboratory procedures Equipment calibration Test reagents Type of antigen retrieval Staff competence Wolff et al 2007

17 Breast cancer 10-20% false positive HER2 tests in the Western world 1-2% false negative HER2 tests Even true for ISH! Paik et al, JNCI 94:852; 2002 Roche et al., JNCI 94:855-7, 2002 Perez et al., JCO 24:3032-8; 2006 Bueno-de-Mesquita et al., Annals Oncol. 21:40-7; 2010

18 Methods Results 694 T1-4N0M0 breast carcinoma patients from 16 hospitals After local examination, central revision ER 5% discordant (kappa 0.85) HER2 4% discordant (kappa 0.81) However 21% false positive!!! Annals of Oncol. 2009

19 The gold standard issue False positive rate FISH: 12%

20 TMA s: approx. 60 breast carcinomas HER2 IHC

21 Data collected IHC + scores from 2 observers for: 4B5, SP3, HERCEPTEST ISH + scores from 2 observers for: Monocolor SISH, dual color SISH Repeat stains and SISH on whole slides for cases showing discrepancy between TMA score and original score

22 Comparison TMA/local result TMA Local HER2 negative HER2 positive HER2 negative HER2 positive

23 Comparison TMA/local result TMA + revision whole section 10 tumoren toch concordant Resteren 20 discordante HER2 gevallen en HER2 988 concordante tumoren (98.0%) negative positive Local HER2 negative HER2 positive

24 Discordant cases 13 local HER2+, revised: HER2- Local ISH procedure unreliable (4) Local ISH score unreliable (2) Local IHC procedure unreliable (3) Local IHC score unreliable (3) (3+, no HER2 gene amplification (1))

25 Nabon Breast Cancer Audit % HER2 positive breast carcinomas <15% in most pathology laboratories

26 Resistance to HER2 targeted therapy Trastuzumab monotherapy in metastatic disease: 20% response rate Neoadjuvant tarstuzumab + chemotherapy: 50% pcr Trastuzumab + chemotherapy in metastatic disease: 70% response rate; most tumors become resistant Adjuvant trastuzumab + chemotherapy: reduction of development of distant metastases by 40-50% No clinically useful biomarkers for response have been identified

27 Summary In the Netherlands, 15% of primary invasive breast carcinomas is HER2 positive In the last 15 years, sensitivity and specificity of HER2 testing has greatly improved Mechanisms for resistance to HER2 targeted therapy are still poorly understood