Figure 2

Comparison of different methods for central assessment of human epidermal growth factor receptor 2 (HER2) overexpression. (A) Five different approaches were used: IHC 3+ or IHC2+/SISH >2.0 (gold standard), HER2 IHC, HER2 SISH ratio, HER2 SISH copy numbers as well as quantitative RT-PCR for evaluation of HER2 mRNA levels. In all approaches the pCR rate was significantly higher in the centrally HER2-positive cases. (P = 0.004, for IHC alone, P <0.0005 for all other comparisons, two-sided Fisher's exact test). (B) Comparison of quantitative HER2 mRNA levels and SISH ratio; pCR cases are marked as dark spots. A total of 11 cases were negative for HER2 mRNA despite an amplification of HER2 by SISH (lower right corner). These cases showed a pCR rate of only 27.3% (three pCRs out of eleven cases). IHC, immunohistochemistry; SISH, silver in situ hybridization; RT-PCR, real-time polymerase chain reaction; pCR, pathological complete response, ypT: tumor stage after neoadjuvant therapy.