The FDA has approved a genetic test for determining whether patients with breast cancer are good candidates for treatment with the drug Herceptin (trastuzumab).

The SPOT-Light HER2 CISH kit is a test that measures the number of copies of the HER2 gene in tumor tissue. The gene regulates the growth of cancer cells.

A healthy breast cell has two copies of the HER2 gene, which signals cells, telling them when to grow, divide, and make repairs. Patients with breast cancer may have more copies of the HER2 gene, causing them to overproduce HER2 protein so more signals are sent to breast cells. As a result, the cells grow and divide far too quickly.

“When used with other clinical information and laboratory tests, this test can provide health care professionals with additional insight on treatment decisions for patients with breast cancer,” said Daniel Schultz, MD, director of the [removed]FDA’s Center for Devices and Radiological Health[/removed].

The test counts the number of HER2 genes in a small sample of removed tumor after a piece is stained with a chemical that causes HER2 genes to change color. The color change is visible under a standard microscope, eliminating the need for more expensive and complex fluorescent microscopes needed to read assays that are currently available. Unlike existing tests, the SPOT-Light allows labs to store the tissue for future reference.

Patients who over produce HER2 protein are typically treated with the drug Herceptin, which targets HER2-protein production and helps halt the growth of HER2 cancer cells.

The FDA based its approval on a study using tumor samples from patients with breast cancer in the United States and Finland, which confirmed the test was effective in determining the amount of HER2 genes.

Invitrogen Corp, Carlsbad, Calif, manufactures sPOT-Light, and Genentech, San Francisco, manufactures Herceptin.