Significance of HER2 low-level copy gain in Barrett's cancer: implications for fluorescence in situ hybridization testing in tissues.
OBJECTIVE
HER2 may be a relevant biomarker in Barrett's cancer. We compared three HER2 laboratory methods, standard fluorescence in situ hybridization (FISH), image-based three-dimensional FISH in thick (16 microm) sections, and immunohistochemistry, to predict patient outcome.


METHODS
Tissue microarray sections from 124 Barrett's cancer patients were analyzed by standard FISH on thin (4 microm) sections and by image-based three-dimensional FISH on thick (16 microm) sections for HER2 and chromosome-17, as well for p185(HER2) by immunohistochemistry. Correlations with clinical and follow-up data were examined.


RESULTS
Only three-dimensional FISH on thick (16 microm) sections revealed HER2 gene copy gain to be associated with increased disease-specific mortality (relative risk, 2.1; 95% confidence interval, 1.06-4.26; P = 0.033). In contrast, standard FISH on thin (4 microm) sections and immunohistochemistry failed to predict clinical outcome. Low-level gain of HER2 occurred frequently in Barrett's cancer (>or=2.5-4.0 HER2 copies, 59.7%; HER2-to-chromosome-17 ratio, >or=1.1-2.0; 61.2%) and defined a subpopulation for patient outcome as unfavorable as HER2 gene amplification [disease-free survival, P = 0.017 (HER2 copies)]. This low-level group was neither definable by standard FISH nor immunohistochemistry. No prognostic significance was found for chromosome-17 aneusomy.


CONCLUSIONS
Low-level copy gains of HER2 define a biologically distinct subpopulation of Barrett's cancer patients. Importantly, these subtle copy number changes are not reliably detected by standard FISH in thin (4 microm) tissue sections, highlighting a thus far unrecognized weakness in HER2 FISH testing. These results should be taken into account for accurate evaluation of biomarkers by FISH and for HER2 FISH testing in tissue sections.
Rauser
Sandra
S
Institute of Pathology , GSF-National Research Center for Environment and Health, Neuherberg, Germany.
Weis
Roland
R
Braselmann
Herbert
H
Feith
Marcus
M
Stein
Hubert J
HJ
Langer
Rupert
R
Hutzler
Peter
P
Hausmann
Michael
M
Lassmann
Silke
S
Siewert
Jörg Rüdiger
JR
Höfler
Heinz
H
Werner
Martin
M
Walch
Axel
A
D000368:Aged; D001471:Barrett Esophagus / Q000150:complications*; D002886:Chromosomes, Human, Pair 17; D004938:Esophageal Neoplasms / Q000235:genetics* / Q000473:pathology; D018628:Gene Dosage; D018734:Genes, erbB-2; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*