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| |  SABCS: Amended Protocol Improves Quality Assurance for HER2 IHC Testing By Coriene E. Hannapel SAN ANTONIO, TX -- December 12, 2002 -- An amended protocol for the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-31 has resulted in drastic improvement of the false-positive rate for HER-2 immunohistochemistry (IHC) testing from 18 percent to 3 percent. Soonmyung Paik, MD, Director of the Division of Pathology for the NSABP, in Pittsburgh, Pennsylvania, United States, presented the study here December 11th at the 25th Annual San Antonio Breast Cancer Symposium. Women participating in NSABP Protocol B-31 have stage II breast cancer with HER-2 overexpression or gene amplification. This multicentre trial was designed to test the advantage of adding Herceptin® (trastuzumab), a recombinant humanised anti-HER-2 monoclonal antibody, to the adjuvant chemotherapeutic regimen of adriamycin and cyclophosphamide followed by paclitaxel (Taxol®). Patients are randomised to adriamycin and cyclophosphamide followed by Taxol® (ACT) or adriamycin and cyclophosphamide followed by Taxol® plus trastuzumab (ACTH). Eligibility for the trial was initially based on results from any local laboratory HER-2 IHC (3+) testing or by fluorescence in situ hybridisation (FISH). Quality assurance measures were built into the B-31 protocol, Dr. Paik said. "Due to substantial cost implications of the treatment, selection of patients based on accurate HER-2 testing is important." The first 104 cases enrolled in B-31 were reviewed and "results of IHC testing by small-volume laboratories were demonstrated to be extremely unreliable," Dr. Paik said. A false-positive rate of 18 percent was demonstrated for IHC testing, with about 20 percent of cases that could not be confirmed as positive (Paik S et al, J Natl Cancer Inst 2002;94:852-4). The protocol was amended, requiring HER-2 IHC testing to be done by laboratories that routinely test large volumes of samples (more than 100 per month) and could demonstrate high concordance between IHC and FISH testing, Dr. Paik said. The FISH test tends to be reliable whether it is done by small- or large-volume laboratories, he added. Since the protocol amendment was instituted, 240 cases have been tested using the Central PathVysionÆ FISH assay. Approval has been granted to 26 laboratories in the United States to date, resulting in reduction of the false-positive rate for IHC testing for HER-2 from 18 percent to 3 percent, Dr. Paik said. This study was supported by grants from the National Cancer Institute, United States, and Genentech.
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