[653] Correlation of Her2 Protein Expression and Gene Amplification between Endoscopic and Surgical Specimens of Gastric Cancer

Cigdem Irkkan, Serdar Balci, Gaye Guler Tezel, Bulent Akinci, Bulent Yalcin, Gulnur Guler. Yildirim Beyazit University, Ankara, Turkey; Hacettepe University, Ankara, Turkey

Background: Reported incidence of Her2 expressing gastric carcinoma is between 6-35%. Recent phase III trial has shown the survival benefit in metastatic gastric carcinoma treated with anti-Her2 therapy. Because of reported heterogenous expression pattern of Her 2 in gastric carcinoma, predictive power of endoscopic biopsies in determining the Her2 status is an important issue. Correlation of Her2 status determined by both immunohistochemistry (IHC) and In situ hybridisation (ISH) techniques in endoscopic biopsies (EB) and gastrectomy specimens (GS) was the aim of this study.
Design: GS and previous EB from 42 gastric tumors in our database are retrospectively searched for their Her2 status by clone:4B5 IHC and Brightfield Dual Silver ISH techniques. Both techniques are performed on the same automated platform (Ventana, Benchmark GX). Heterogenity of Her2 IHC staining was categorised as dispersed or clustered in both EB and GS.

Comparison of IHC results in EB versus GS
  0, 1+2+3+Total
 0, 1+322034
IHC EB2+1113

Among 5 (11.90%) discordant results; cause was heterogenity in 3 (dispersed in 2, clustered in 1). Cause can be speculated as preanalytical in the other 2. Satisfactory reaction with ISH technique could not be achieved in some of the EB-GS pairs. Therefore only 28 of 42 EB-GS pairs were available to compare.

Comparison of ISH results in EB versus GS
ISH EBBorderline1001

Number of discordant results decreased with ISH (7.14%); and heterogenity was the cause in both of them (1 dispersed, 1 clustered). Discordance rate with IHC was 16.66%, with ISH was 7.14%.
Conclusions: Her2 status heterogenity was the major cause of discordant results between EB and GS. Dispersed heterogenity is more effective than clustered in our cases. In 14 (33%) of our 42 cases, because of preanalytical variability of mainly fixation time, satisfactory reaction could not be achieved with ISH. IHC seems to be more effective in cases with preanalytical problems. Discordant results in EB did not cause overdiagnosis in any case which would have resulted in unnecessary treatment, however one patient with a negative Her-2 result in EB both by IHC and ISH, was found Her-2 positive in GS. Our results support the simultaneous use of ISH and IHC for Her-2 testing in gastric cancer.
Category: Gastrointestinal

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 101, Wednesday Afternoon


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