Real-time RT-PCR: a complementary method to detect HER-2 status in breast carcinoma

The option to treat patients presenting with HER-2 overexpressed invasive breast carcinoma with Herceptin requires quantitative determination of the HER-2 status. The aim of this study was to retrospectively evaluate the HER-2 mRNA expression levels using quantitative real-time RT-PCR (Q-RT-PCR) in tissue samples from 44 primary breast carcinomas and compare the results with immunohistochemistry (IHC). To determine the cut-off for altered mRNA expression, a normalized HER-2 expression value was determined for 20 normal breast tissue RNAs. Gene expression was categorized into three groups: normal expression (mRNAs <3); moderate overexpression (3 < or = mRNAs < 10) and strong overexpression (mRNAs < or =10). More than 38% (17/44) displayed strong overexpression, 25% (11/44) moderate and 36.3% (16/44) normal expression. Compared to IHC, only 7/44 cases were slightly discordant: strong mRNA overexpression/2+ protein staining (1 case), moderate overexpression/ 1+ (3 cases) and moderate overexpression/3+ (3 cases). These results show a high concordance rate (84%) between Q-RT-PCR and IHC (p < 10(-4)). We conclude that Q-RT-PCR is a useful complementary method for determination of the HER-2 status.