Prospective multi-centre study to validate chromogenic in situ hybridisation for the assessment of HER2 gene amplification in specimens from adjuvant and metastatic breast cancer patients.
OBJECTIVE
As HER2 status is a strong predictor of the response to trastuzumab, clinical guidelines recommend that all breast tumours are first evaluated for HER2 protein expression by immunohistochemistry (IHC) followed by confirmatory testing for HER2 gene amplification using fluorescence in situ hybridisation (FISH) for 2+ cases. Alternatively, chromogenic in situ hybridisation (CISH) offers a simpler, less expensive approach to detect HER2 amplification.


METHODS
In this prospective, multi-centre study, based on the largest dataset for HER2 testing in Germany to date, we evaluated the concordance between FISH and CISH in 399 samples from adjuvant and metastatic breast cancer patients. Tumour specimens from routine diagnostic practice were analysed by IHC, FISH and CISH in four reference centres.


RESULTS
FISH and CISH results were strongly concordant (κ = 0.83), with 95% of cases showing agreement. Despite variable IHC scoring across testing centres, complete consensus among the three methods was observed for 246 cases, representing 91% of all IHC positive (3+) or negative (0/1+) cases. Confirmatory testing of 132 IHC equivocal (2+) cases also yielded highly concordant results between FISH and CISH.


CONCLUSIONS
These data validate CISH for the assessment of HER2 gene amplification in breast tumours and, confirm CISH as a valid alternative to FISH in HER2 testing.
Riethdorf
Sabine
S
Institute of Tumor Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Hoegel
Bernhard
B
John
Birgit
B
Ott
German
G
Fritz
Peter
P
Thon
Susanne
S
Loening
Thomas
T
Pantel
Klaus
K
D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D001943:Breast Neoplasms / Q000737:chemistry* / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D002863:Chromogenic Compounds; D005260:Female; D018734:Genes, erbB-2; D005858:Germany; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization / Q000379:methods; D017404:In Situ Hybridization, Fluorescence; D008875:Middle Aged; D021141:Nucleic Acid Amplification Techniques / Q000379:methods; D011446:Prospective Studies; D000068878:Trastuzumab
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D002863:Chromogenic Compounds; D000068878:Trastuzumab
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