Identifying Who Will Benefit from Herceptin®

The Oncologic Drugs Advisory Committee of the U.S. Food and Drug Administration (FDA) has approved a gene-detection test called FISH (fluorescence in situ hybridization) that can help identify which women with metastatic breast cancer will benefit from Herceptin therapy.

Herceptin received its original FDA approval in September 1998 for use in women with metastatic breast cancer who have tumors that "overexpress" (produce an overabundance of) the HER2 protein. Herceptin is designed specifically to block the cancerous growth-promoting products of the excessive number of HER2 genes. It is indicated for treatment of patients both as first-line therapy in combination with paclitaxel, and by itself as a second- and third-line therapy.

FISH is a diagnostic test used to determine the number of HER2 genes in a patient's breast cancer cells. FISH testing measures the number of genes in each cell, using fluorescent dye so the HER2 genes can be seen and counted with a special microscope. More than the normal two HER2 genes per cell are present in HER2 positive breast cancer.

The research that led to the FDA committee's recommendation for approval included a study involving tissue samples from metastatic breast cancer patients. Investigators compared the results of the gene-based FISH test (trade name PathVysion), with the current standard HER2 immunohistochemical (IHC) protein test.

The data showed that gene tests using FISH to diagnose HER2-positive breast cancer were reliable, accurate and agreed with the standard IHC protein test in 88 percent of the cases.

The Oncologic Drugs Advisory Committee recommended sending this new information about the FISH test to physicians who are currently prescribing Herceptin treatment for their breast cancer patients. The FDA is not bound by its committee's recommendation, but the agency usually follows its advice.

SOURCES:
Meeting of the Oncologic Drugs Advisory Committee, U.S. Food and Drug Administration, December 5, 2001 (http://www.fda.gov)
Genentech, Inc. (http://www.genentech.com)

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