Table 2.
Comparison of Average HER2 Gene Copy Numbers per Tumor Cell and HER2 Fluorescence In Situ Hybridization (FISH) Ratios With HER2 Protein Expression by Either HercepTest or 10H8 Immunohistochemistry (IHC) Scores in 7526 Breast Cancers
| Association of Average HER2 Gene Copy Number and HER2 FISH Ratios With HER2 Protein by IHC Scores | |||||||
|---|---|---|---|---|---|---|---|
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| |||||||
| HER2 FISH Assay Results | IHC Score, No. (%)a | ||||||
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| HER2 FISH Ratios | Average HER2 Copy Number per Cell | IHC 0 | IHC 1+ | IHC 2+ | IHC 3+ | Totals, No. (%) | P Valueb |
|
| |||||||
| — | <4.0 | 3612 (62.2) | 1977 (34.1) | 204 (3.5) | 12 (0.2) | 5805 (77.1) | .01 |
| — | 4.0–5.9 | 202 (37.2) | 229 (42.2) | 102 (18.8) | 10 (1.8) | 543 (7.2) | |
| — | 6.0–7.9 | 44 (26.4) | 46 (27.5) | 60 (35.9) | 17 (10.2) | 167 (2.2) | |
| — | 8.0–9.9 | 15 (12.9) | 28 (24.1) | 47 (40.5) | 26 (22.4) | 116 (1.5) | |
| — | ≥10.0 | 16 (1.8) | 54 (6.0) | 259 (28.9) | 566 (63.2) | 895 (11.9) 7526 | |
| <2.0 | — | 3753 (60.9) | 2157 (35.0) | 238 (3.9) | 19 (0.3) | 6167 (81.9) | .009 |
| 2.00–5.0 | — | 119 (22.1) | 122 (22.6) | 213 (39.5) | 85 (15.8) | 539 (7.2) | |
| 5.01–10.0 | — | 17 (2.8) | 40 (6.6) | 177 (29.2) | 372 (61.4) | 606 (8.1) | |
| >10.0 | — | 0 (0) | 15 (7.0) | 44 (20.6) | 155 (72.4) | 214 (2.8) | |
a
When data from both HER2 immunohistochemical assays, 10H8 and HercepTest, were available, the 10H8 assay result was used.
b
P value based on the asymptotic distribution of the Wald statistic for the Spearman correlation coefficient.24