1. Moving Toward Personalized Treatment for Gastric Cancer: Role of HER2 Testing Frédérique Penault-Llorca, MD, PhD Professor of Pathology Centre Jean Perrin Université d'Auvergne Clermont Clermont-Ferrand, France

2. HER2 Testing in Gastric Cancer: Common Characteristics and Unique Features HER2 testing algorithm Tissue collection Tissue morphology Turn-around time Scoring criteria Multiple biopsies (6–8) recommended Representative samples of surgical specimens HER2 = human epidermal growth factor receptor 2

3. The Need for Multiple Biopsies Images property of Frédérique Penault-Llorca, MD, PhD.

4. HER2 testing algorithm Tissue collection Tissue morphology Turn-around time Scoring criteria Multiple biopsies (6–8) recommended Representative samples of surgical specimens High level of tumor heterogeneity (small HER2-positive foci) Screening of the entire specimen required for FISH FISH = fluorescence in situ hybridization HER2 Testing in Gastric Cancer: Common Characteristics and Unique Features

5. Tumor Heterogeneity Images property of Frédérique Penault-Llorca, MD, PhD.

6. Complete, Basolateral or Lateral Membranous Staining HER2-positive gastric and gastroesophageal junction tumors may show complete, basolateral, or lateral membranous staining Basolateral/lateral staining occurs due to the structure of low-grade gastric adenocarcinoma cells Hofmann M et al. Histopathology. 2008;52:797-805. Image property of Frédérique Penault-Llorca, MD, PhD.

7. HER2 testing algorithm Tissue collection Tissue morphology Turn-around time Scoring criteria Multiple biopsies (6–8) recommended Representative samples of surgical specimens High level of tumor heterogeneity (small HER2-positive foci) Screening of the entire specimen required for FISH Similar to breast cancer Primary IHC testing HER2-positive: IHC 3+ or IHC 2+/FISH+ Bright-field methodologies preferred HER2 Testing in Gastric Cancer: Common Characteristics and Unique Features IHC = immunohistochemistry

8. 0 FISH +– Eligible for trastuzumab 1+2+3+ IHC Patient tumor sample Recommended HER2 Testing Algorithm in Metastatic Gastric and Gastroesophageal Junction Cancer Trastuzumab EU SmPC: http://www.ema.europa.eu/humandocs/PDFs/EPAR/ Herceptin/emea-combined-h278en.pdf.

9. HER2-Positivity Rate in Advanced Gastric Cancer EMA licensed population (IHC 2+/FISH+ or IHC 3+) Exploratory analysisToGA population Eligible for ToGA (IHC 3+ and/or FISH+) 78% 22% 78% 16% Not eligible for ToGA Not eligible for ToGA IHC 0/FISH+ or IHC 1+/FISH+ 6% Chung H et al. Eur J Cancer Suppl. 2 009; 7:364.

10. HER2 Testing in Gastric Cancer: Common Characteristics and Unique Features HER2 testing algorithm Tissue collection Tissue morphology Turn-around time Scoring criteria Multiple biopsies (6–8) recommended Representative samples of surgical specimens High level of tumor heterogeneity (small HER2-positive foci) Screening of the entire specimen required for FISH Similar to breast cancer Primary IHC testing HER2-positive: IHC 3+ or IHC 2+/FISH+ Bright-field methodologies preferred Strong basolateral, lateral or complete membrane staining in ≥10% of tumor cells is considered positive (IHC) No percentage cut-off for biopsies

11. HER2 Scoring Criteria in Gastric Cancer Surgical specimen staining pattern Biopsy specimen staining pattern ScoreAssessment No reactivity or membranous reactivity in < 10% of tumor cells No reactivity or no membranous reactivity in any tumor cell 0 Negative Faint ⁄ barely perceptible membranous reactivity in ≥ 10% of tumor cells; cells are reactive only in part of their membrane Tumor cell cluster with a faint ⁄ barely perceptible membranous reactivity irrespective of percentage of tumor cells stained 1+ Negative Weak to moderate complete basolateral or lateral membranous reactivity in ≥ 10% of tumor cells Tumor cell cluster with a weak to moderate complete basolateral or lateral membranous reactivity irrespective of percentage of tumor cells stained 2+ Equivocal Strong, complete basolateral or lateral membranous reactivity in ≥ 10% of tumor cells Tumor cell cluster with a strong, complete basolateral or lateral membranous reactivity irrespective of percentage of tumor cells stained 3+ Positive Trastuzumab EU SmPC: http://www.ema.europa.eu/humandocs/PDFs/EPAR/ Herceptin/emea-combined-h278en.pdf.

12. HER2 Testing in Gastric Cancer: Common Characteristics and Unique Features HER2 testing algorithm Tissue collection Tissue morphology Turn-around time Scoring criteria Multiple biopsies (6–8) recommended Representative samples of surgical specimens High level of tumor heterogeneity (small HER2-positive foci) Screening of the entire specimen required for FISH Similar to breast cancer Primary IHC testing HER2-positive: IHC 3+ or IHC 2+/FISH+ Bright-field methodologies preferred Strong basolateral, lateral or complete membrane staining in ≥10% of tumor cells is considered positive (IHC) No percentage cut-off for biopsies Turn-around times should not exceed 5 working days (metastatic gastric cancer progresses very quickly) Need for a multidisciplinary approach

13. Patient Medical technician Oncologist/ Gastroenterologist Pathologist Surgeon/ Endoscopist Tissue removal, orientation & storage until collection Sample processing Test methodology Test interpretation and reporting Request appropriate tests & arrange sample collection Successful HER2 Testing Requires a Multidisciplinary Approach

14. HER2 Testing in Gastric Cancer: Conclusions All patients with gastric cancer should be tested for HER2 Patients with HER2-positive metastatic gastric cancer are eligible to receive trastuzumab Testing should be performed by experienced pathologists Quality assurance/control procedures should be followed to ensure quality of HER2 testing