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The Daily Wildcat

The Daily Wildcat

 

City among first for new cancer test

Tucson is one of the first cities in the country to adopt a new breast cancer testing method that shortens the waiting time between diagnosis and treatment.

The HER2 Dual ISH assay test was developed in Tucson by Ventana Medical Systems, Inc. and was approved by the U.S. Food and Drug Administration. The breast cancer method tests for amplification of a specific gene called HER2, said Dr. Jennifer Thorn, assistant professor in the Department of Pathology. Thorn will validate and interpret the test.

“When that specific gene is amplified, a certain percentage of those patients will respond to a specific drug (Herceptin),” Thorn said. “Those patients also have a slightly different prognosis and their tumors tend to be more aggressive and come back more quickly than traditional therapies.”

On a glass slide, doctors are able to “stain” the DNA of the specific gene and evaluate how many copies of it are present in the cell, she said. A normal cell would have two copies, while an abnormal one would have more.

The method being used before was the FISH, or fluorescence in situ hybridization test, where doctors used a fluorescent microscope to map genetic material in a person’s cells. The test reveals the number of copies of the HER2 genes, genes that serve as receptors that can receive signals that stimulate breast cancer cell growth. The HER2 test allows them to use a regular bright field microscope, which will cut down the waiting time for results.

The FISH test took between four to seven days, but the HER2 method is expected to take two to three days for results. Thorn said this new test is still being validated but she hopes it will be available for clinical testing at the University Medical Center–University Campus by next month.

“The other advantage of it from our standpoint is that we can keep the slides for archival,” she said. “Being a teaching hospital, we can share them with oncologists and surgeons so everyone can see them, whereas if it’s on a fluorescent microscope it’s a little bit harder to do that.”

Thorn added that the fluorescent tissue fades and it can’t be looked at later on.

The standard practice for patients with breast cancer is to do an immunohistochemistry screening test for the HER2 gene. Immunohistochemistry is a process to detect proteins in a certain cell. This is used to determine the therapy methods.

“It’s really part of the protocol for all breast cancers,” Thorn said. “If the immunohistochemistry shows us that it’s indeterminate or that it’s positive, we test it by FISH.”

The HER2 test is better in the sense that it will shorten the turn-around time and is easier to interpret than FISH testing, she said.

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