[235] Concordance between local labs and a central lab using FISH and IHC for HER2 testing.

Conclusions: These results are consistent with reports of inaccuracies in the determination of HER2 status by IHC and suggest that IHC performed at experienced labs demonstrating proficiency may yield more accurate results than IHC performed at local labs. In this study local IHC failed to identify 15% of 3+ patients that were eligible for enrollment. FISH testing identified another 16% of patients that were not identified by either central or local IHC. Based on these results in patients who have IHC scores <3+ consideration should be given to retesting with FISH. Additional data are needed to determine reproducibility of FISH. Preliminary data suggest that there may be higher reproducibility with FISH than IHC.