The U.S. Food and Drug Administration has approved a novel 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. This gene regulates the growth of cancer cells. A healthy breast cell has two copies of the HER2 gene, which sends a signal to cells, telling them when to grow, divide and make repairs. Patients with breast cancer may have more copies of this HER2 gene, prompting them to overproduce HER2 protein so that more signals are sent to breast cells. As a result, the cells grow and divide much 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, M.D., director of the FDA’s Center for Devices and Radiological Health.
The SPOT-Light test counts the number of HER2 genes in a small sample of removed tumor. The removed piece is stained with a chemical that causes any HER2 genes in the sample to change color. This color change can be visualized under a standard microscope, eliminating the need for the more expensive and complex fluorescent microscopes required to read assays already on the market. 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. This helps to stop the growth of HER2 cancer cells. The US FDA based its approval of the SPOT-Light test on a study using tumor samples from patients with breast cancer in the United States and Finland. These studies confirmed that the test was effective in determining how many HER2 genes were in these patients. SPOT-Light is manufactured by Invitrogen Corp. of Carlsbad, Calif. Herceptin is manufactured by Genentech, of San Francisco, Calif.