FDA OKs New Breast Cancer Gene Test

SPOT-Light Test May Help Determine Which Patients Are Good Candidates for Breast Cancer Drug Herceptin

Medically Reviewed by Louise Chang, MD on July 08, 2008
From the WebMD Archives

July 8, 2008 -- The FDA has approved a new genetic test for determining which breast cancer patients are good candidates for treatment with the drug Herceptin.

The SPOT-Light HER2 CISH kit is a test that measures the number of copies of the HER2 gene in tumor tissue. The HER2 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," Daniel Schultz, MD, director of the FDA's Center for Devices and Radiological Health, says in an FDA news release.

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. The FDA notes that, unlike existing tests, the SPOT-Light allows labs to store the tissue for future reference.

Patients who overproduce 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 FDA based its approval of the SPOT-Light test on a study using tumor samples from patients with breast cancer in the U.S. and Finland. These studies confirmed that the test was effective in determining how many HER2 genes were in these patients.

SPOT-Light is made by Invitrogen Corp. of Carlsbad, Calif.