New Test Evaluates Toxicity Risk from Chemo
Myriad Genetics, Incorporated launched a novel diagnostic tool on July 26th, the TheraGuide 5-FU, as described in a press release from the company. The tool pinpoints the patients most likely to suffer from toxic reactions to 5-Fluorouracil (5-FU).
The test evaluates the presence of genetic variations on two different genes, TYMS and DYPD, that are associated with an increased risk of 5-FU toxicity. Variations in TYMS can limit the availability of the enzyme that 5-FU binds to or cause overproduction of that same enzyme. The result of limited enzyme production is unbound 5-FU, increasing drug toxicity. Alternatively, if the enzyme is overproduced, it mitigates the therapeutic effects of the agent.
The DYPD gene produces an enzyme that metabolizes 5-FU. Alterations to this gene moderate how long 5-FU stays in the body. Decreased ability to metabolize the drug increases the time of the anti-malignant effects. This prolonged exposure to chemotherapy increases the risk for toxicity effects.
This chemotherapeutic agent is commonly used in treatment regimens for solid tumors; almost half a million U.S. residents receive 5-FU each year. About thirty percent of patients who receive a chemotherapy regimen that includes 5-FU experience severe to life-threatening toxicity from the drug, which is then dose-limiting. Toxic effects can result in cognitive deficits, stomatitis, and hand-foot syndrome, among other reactions.
Assessment of cancer patients with this test may help guide treatment planning, in the event that multiple chemotherapy regimens exist with essentially equivalent efficacy. Clinicians may also alter 5-FU doses based on an identified anomaly in either of the genes.
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July 27, 2007 Related topics: Hematology & Oncology