HER-2/neu assessment in breast cancer by immunohistochemistry and fluorescence in situ hybridization: comparison of results and correlation with survival

HER-2/neu immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) results guide breast cancer therapy; however, few studies compared the results and no published studies have correlated them with patient outcome. We compared results, cost, and turnaround time in 117 archival, invasive breast carcinomas and compared 50-month survival in 65 of these cases using commercial HER-2/neu IHC and FISH assays. Twenty-one of 112 FISH (19%) and 33 of 117 IHC cases (28%) were positive. Concordance was high overall (88%; 98 of 112 cases) and in IHC 3+ cases (88%; 14 of 16 cases) but low in IHC 2+ cases (35%; six of 17 cases). Survival correlated with IHC results in 3+ cases (P =.02) and FISH cases with signal ratio greater than 4.0 (P =.03), but not in IHC 2+ cases (P=.7). Cost and turnaround time were greater for FISH. IHC is appropriate for initial HER-2/neu assessment; however, patients with tumors scored less than 3+, particularly those interpreted as 2+, would benefit from FISH to more accurately assess HER-2/neu status and avoid inaccurate prognostication and inappropriate treatment.