Genetic Test for Patients with Breast Cancer Gains Federal Approval

Except for skin cancers, breast cancer is the most common cancer among American women. It is estimated that in 2008 approximately 182,460 new cases of invasive breast cancer will be diagnosed among women in the United States. Depending on the risk factors and the stage of the tumor, women diagnosed with breast cancer have several treatment options such as surgery, radiation, chemotherapy, hormonal therapy, or targeted biologic therapy. Some women may be candidates to receive Herceptin (trastuzumab) drug therapy, and a new test approved by the FDA on July 8 may make it easier to determine who these women are.

A healthy breast cell has two copies of the HER2 gene that sends signals to cells, telling them when to grow, divide, and make repairs. However, patients with breast cancer may have more copies of the HER2 gene, prompting the overproduction of HER2 protein so that more signals are sent to breast cells. This results in the cells growing and dividing too quickly. Patients who overproduce HER2 protein are usually treated with Herceptin, which targets HER2 protein production and helps stop the growth of HER2 cancer cells.

The genetic test, called SPOT-Light HER2 CISH, measures the number of copies of the HER2 gene. For the SPOT-Light test, a small sample of removed tumor is stained with a chemical that causes any HER2 genes 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 the lab to store the tissue for future reference. "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, M.D., director of the FDA's Center for Devices and Radiological Health said in the news release.

The 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.

The SPOT-Light test is made by Invitrogen Corp. of Carlsbad, California.