Testing for HER2-Positive Breast Cancer

Hatem Soliman, MD, an associate member of the breast oncology program, and medical director of the clinical trials office, Moffitt Cancer Center, explains how to test for HER2 status in patients with breast cancer.

According to Soliman, there are 2 clinical standards and ways that are used to determine whether a patient is HER2-positive or HER2-negative. Once a tissue sample has been taken from the patient, investigators can use either an immunohistochemistry test or a fluorescence in situ hybridization test to test for HER2-status.

When utilizing the immunohistochemistry test, experts are able to determine the amount of HER2 protein that is found in the cancer cells of a patient. In the fluorescence or a chromogenic dye in situ hybridization test, experts are able to see whether or not there are amplifications in the HER2 gene in the cancer cells. This test also looks for extra copies of the HER2 gene in patients.

If HER2 protein levels are higher than normal or there are extra copies of the HER2 gene found, patients most likely have HER2-positive cancer. If the results show normal amounts of HER2 protein or genes, the patient probably has HER2-negative cancer.

If the results with 1 of the tests are not clear, experts may turn to the other type of test in order to obtain a more definite result.

Transcription:

0:08 | The clinical standard to test for HER2 status, in most cases, involves a combination of immunohistochemistry, testing for overexpression of the HER2 protein, and the other method that we use as well is based on a either a fluorescence or a chromogenic dye in situ hybridization test, to check to see if there are amplifications of the HER2 gene that are detected within the nucleus of the cells that are counted.

0:42 | So either by having that amplification of HER2 on the [in situ hybridization] tests or overexpression of the protein on the immunohistochemistry test, then we would classify those patients as HER2-positive for targeted therapy.