[728] Her2 Status in Gastric Adenocarcinoma: A Comparison of Immunohistochemistry (IHC), Fluorescent In-Situ Hybridization (FISH) and Dual Color Silver In-Situ Hybridization (SISH) Methods.

Chen Zhou, David Huntsman, Beverly Carter, Tom Thomson, Julie Lorette, Sylvia Lee, Lynda Bell, Francine Aubin, Ryan Woods, Howard Lim, Sharlene Gill. British Columbia Cancer Agency, University of British Columbia, Vancouver, Canada

Background: Testing of Her 2 status of gastric adenocarcinoma is now being requested as a routine pathology test as trastuzumab is a potential treatment option for Her2 positive gastric adenocarcinoma. However, reports about Her 2 testing in gastric adenocarcinoma are few and standards for Her2 testing in gastric adenocarcinoma are not yet established.
Design: A total of 87 patients with gastric adenocarcinoma either from the British Columbia Cancer Agency tumor registry or from an ongoing prospective clinical trial were identified. Formalin fixed biopsy or resection tissues containing gastric adenocarcinoma were used for IHC staining for Her2 protein expression (Ventana®,4B5 antibody), for FISH testing (Abbott, PathVysion®) and for dual color SISH testing (Ventana®, Inform Her2).
Results: When the ASCO/CAP guideline for Her2 testing in breast cancer is used, Her2 protein expression positive rate is 12.7% (IHC 3+, 7 cases; and IHC 2+ with gene amplification by FISH or SISH, 4 cases), Her2 gene amplification rate by FISH is 14.9% (13/87 cases) and by SISH is 13.8% (12/87 cases). When the modified ASCO/CAP guideline, as defined by the manufacturer's package insert is used, Her2 protein expression positive rate is 19.5% (IHC 3+, 11 cases; and IHC 2+ with gene amplification by FISH, 6 cases) or 18.4% (IHC 3+, 11 cases; and IHC 2+ with gene amplification by SISH, 5 cases), Her2 gene amplification rate by FISH is 18.4% (16/87 cases) and by SISH is also 18.4% (16/87 cases). There is good concordance between FISH and SISH, IHC and FISH and IHC and SISH (table 1).

Table 1: Concordance between Analysis Methods
 FISH vs. SISHIHC vs. FISHIHC vs. SISH
Negative concordance95.6%98.0%96.4%
Positive concordance90.0%81.8%81.8%


Compared to FISH, dual color SISH has some technique advantages as it uses bright field and has shorter turn around time (1 day vs. 7 days).
Conclusions: Her2 status of gastric adenocarcinoma can be reliably tested using the ASCO/CAP guideline or the modified ASCO/CAP guideline for Her2 testing in breast cancer. SISH and FISH are highly concordant. Combined with IHC, either FISH or SISH can be used as a reliable method for testing of Her2 gene status in gastric adenocarcinoma.
Category: Gastrointestinal

Tuesday, March 1, 2011 11:00 AM

Platform Session: Section E, Tuesday Morning

 

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