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| |  SABCS: Fluorescence In Situ Hybridisation Assay More Accurate in Predicting Response to Gene Therapy in Breast Cancer By Robert H. Carlson SAN ANTONIO, TX -- December 12, 2001 -- Women with breast cancer can be more accurately identified as candidates for gene therapy with Herceptin (trastuzumab, Genentech Inc.) when a fluorescence in situ hybridisation (FISH) assay is used, compared with women whose gene status was obtained using a standardized, semi-quantitative immunohistochemistry (IHC) assay. This finding is according to a study presented here at the 24th Annual San Antonio Breast Cancer Symposium. These two assays were compared in a retrospective study conducted by researchers from Genentech, Inc., the manufacturer of Herceptin, along with researchers from the University of Southern California and University of California at Los Angeles (UCLA) School of Medicine, in Los Angeles, California. In his presentation here, Robert Mass, MD, Associate Director of Oncology at Genentech Inc., and first author of this paper, said the pivotal trial for Herceptin has already established that women with metastatic breast cancer respond better when Herceptin is added to their chemotherapy than do women who receive chemotherapy alone. The response rates for that pivotal trial were 50 percent for women taking Herceptin plus chemotherapy, compared to 32 percent for those on chemotherapy alone (p=0.003). Women were enrolled in the pivotal trial if they were identified as having having human epidermal growth factor receptor 2 (HER2) gene overexpression, as measured by the IHC assay. In the new study, archived tissue samples from the original study were re-analysed using the FISH assay. Amplification of the HER2 gene was detected in 76 percent of the 451 evaluable samples using a PathVysion dual-probe fluorescence in situ hybridisation (FISH) assay system. The researchers determined that women who were HER2-positive by FISH and received Herceptin had a 54 percent response rate, compared with 30.8 percent of the women who were HER2-positive by FISH but did not receive Herceptin (p<0.0001). Women who were HER-2-negative by FISH assay had approximately the same response rate regardless of whether they received Herceptin -- 38.0 percent responded after receiving Herceptin compared to 37.5 percent for those who did not receive Herceptin. The addition of Herceptin to chemotherapy in the FISH-positive group also provided a significant survival benefit (OR=0.71; 95% CI=0.54-0.92; p=0.009), which was not detected in the FISH-negative group, Dr. Mass said. Genentech Inc, does not have a financial interest in the FISH assay, but only an interest in assuring that women who might respond to Herceptin are accurately identified, he added. Patient selection based on HER2 amplification by FISH may provide improved clinical and survival benefits from Herceptin therapy compared to selection by IHC, Dr. Mass concluded.
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