Human Epidermal Growth Factor Receptor-2(HER-2) expression in Sri Lankan gastric adenocarcinoma patients: An analysis of the concordance of HER2 expression and survival based on silver in-situ hybridization (SISH)

Background: Accurate HER2 status is crucial for gastric adenocarcinoma (GC) patient selection for antiHER2 therapy. It is assessed immunohistochemically (IHC) for protein expression, and by silver in-situ hybridization (SISH) for gene copy number. This study aimed to evaluate the concordance of HER2 status by IHC/SISH analyses and HER2-SISH based survival.Methods: This prospective study includes 145 GC’s (excluding gastro-oesophageal-junction tumours) from the National Hospital of Sri Lanka with defined demographic, clinical-radiological-pathological characteristics. HER2-IHC was assessed by DAKO A0485, RealTM Envision system and interpreted using Ruschoff criteria. HER2-SISH was assessed with INFORM HER2 dual ISH DNA Probe Cocktail. Concordance between HER2 IHC/SISH results was determined by Cohens kappa statistics. The association between the survival and HER2-SISH positivity was evaluated using the cox-regression method. Adjustments were done for age, gender, Lauren classification, tumour location and the tumour staging.Results: Of the 69 gastrectomies and 76 biopsies, 8.3% (n = 12) were HER2-IHC positive (n = 7, + 2 and n = 5, + 3). HER2-SISH positivity was 4.8 % (n = 7). All IHC + 3 were SISH positive, while two + 2 cases were SISH positive. Concordance for IHC 0, + 1, +3 were 100%. There was a significant overall correlation (kappa = 0.72, p < 0.001) between HER2-IHC and HER2-SISH indicating substantial concordance. The mean overall survival of HER2-SISH negative and positive patients were 41.7 (0-210) and 14.6 (3–51) weeks respectively, after a mean duration of patient follow up for 40.4 weeks (range 0-210). Survival was relatively lower (p = 0.001) in the group with HER2-SISH positivity.Conclusion: HER2-IHC was well concordant with HER2-SISH for 0, + 1, +3 scores and could be used for treatment and prognostication in low resource settings, where SISH facility is unavailable. HER2-IHC + 2, without gene amplification may be due to transcriptional activation by other genes or post-transcriptional events, mandating further evaluation by SISH. Survival of GC patients is significantly affected by HER2-SISH positive status.

HER2 Heterogeneity in Gastroesophageal Cancer Detected by Testing Biopsy and Resection Specimens

Context.— In advanced gastric, esophageal, and gastroesophageal junction adenocarcinomas (GE-GEJ-AC) that overexpress ERBB2 (erb-b2 receptor tyrosine kinase 2 or HER2), anti-HER2 monoclonal antibody therapy confers survival benefit. To select patients for treatment, HER2 expression and gene amplification are evaluated by immunohistochemistry (IHC) and in situ hybridization. Objective.— To determine whether GE-GEJ-AC tested for HER2 on biopsy specimens of a primary tumor show different IHC scores and/or HER2 amplification by in situ hybridization in matched resection specimens, potentially changing therapy eligibility. Design.— Immunohistochemistry and silver in situ hybridization were performed in biopsy and/or resection specimens from 100 patients. HER2 testing was performed in matched resection and biopsy specimens of 15 cases to determine whether GE-GEJ-AC with IHC scores of 0, 1+, and 2+ in biopsy and resection specimens had different IHC and silver in situ hybridization results. Results.— The IHC 3+ cases showed HER2 amplification in 4 of 5 cases (80%), and IHC scores of 0, 1+, and 2+ showed 3.5%, 14.3%, and 23.5% HER2 amplification by silver in situ hybridization. Among the 15 paired biopsy and resection specimens, 9 (60%) had at least pT2 stage GE-GEJ-AC with HER2 IHC scores of 0, 1+, or 2+ in the biopsy, and 2 of those 9 cases (22%) had IHC 3+ and HER2 amplification by silver in situ hybridization on the resection specimen. Conclusions.— Our data suggest that HER2 testing should be repeated on resection specimens of GE-GEJ-AC with HER2 IHC scores of negative (0 and 1+) or equivocal (2+) and in situ hybridization amplification negative biopsy specimen results to evaluate for HER2 heterogeneity when patients are being considered for anti-HER2 therapy.