In step with the trend toward more selective use of chemotherapy, Labcorp has launched an expanded version of its DPYD Genotype test, which helps identify cancer patients at increased risk for severe side effects from fluoropyrimidine-based drugs. The test is now the only offering, from a national laboratory provider, that detects all Tier 1 and Tier 2 DPYD variant alleles recommended to be tested for by the Association for Molecular Pathology.
The DPYD gene encodes the enzyme DPD, which metabolizes more than 80% of 5-FU. Patients with reduced or absent DPD activity can experience serious, potentially life-threatening side effects, including diarrhea, neutropenia, and neurotoxicity when given fluoropyrimidines 5-FU or capecitabine.
Such pharmacogenomic (PGx) testing is used to help identify patients who are at greater risk for adverse drug reactions from certain treatments based on their genetic makeup. Once a chemotherapy regimen is recommended, PGx testing can help guide treatment decisions and reduce the risk of toxicity. DPYD testing is one of the most well-established examples of PGx.
“Pharmacogenomic testing is typically incorporated early in the treatment process, once a chemotherapy plan has been established, to give clinicians information about a patient’s inherited ability to metabolize certain medications or respond to them,” Annette Taylor, PhD, MS, told Inside Precision Medicine. She is associate vice president, strategic director, pharmacogenomics, Labcorp.
Fluoropyrimidines are one of the most widely used chemotherapy agents for colorectal, pancreatic, gastrointestinal, breast, and head and neck cancers. However, up to 9% of cancer patients carry DPYD variants that can negatively affect their ability to break down such drugs. That variant contributes to an estimated 1,300 deaths in the U.S. each year. By identifying the full range of Tier 1 and Tier 2 DPYD variants, the new test helps reduce the risk that vulnerable patients will receive the treatment.
“Advances in pharmacogenomics are reshaping cancer care,” said Marcia Eisenberg, PhD, chief scientific officer at Labcorp. “Our expanded DPYD test identifies patients at risk for severe toxicity before treatment begins, supporting safer, more personalized care.”
The U.S. Food and Drug Administration (FDA) recently updated its product labeling for 5-FU and capecitabine, which includes a Boxed Warning about the risk of severe adverse reactions or death in patients with complete DPD deficiency. The agency also advises testing for DPYD variants before treatment with 5-FU or capecitabine unless immediate treatment is necessary and recommends avoiding use of these drugs in patients with certain homozygous or compound heterozygous DPYD variants associated with complete DPD deficiency.
In addition, recent updates to National Comprehensive Cancer Network (NCCN) guidelines for colon cancer and other relevant indications reference these Boxed Warnings and the recommendation for DPYD testing. Further, Clinical Pharmacogenomics Implementation Consortium (CPIC) guidelines recommend adjusting or avoiding treatment based on a patient’s DPYD metabolizer status as determined by DPYD testing.
“There are other pharmacogenomic tests available beyond DPYD testing that can provide clinically actionable information for certain therapies and treatment settings. Common tests include UGT1A1 genotyping for irinotecan and TPMT/NUDT15 testing for thiopurines,” Taylor said.
Other tests offered by Labcorp include the UGT1A1 Irinotecan Toxicity test, which helps guide chemotherapy with irinotecan, commonly used for metastatic colon and rectal cancer. Labcorp also offers the TPMT and NUDT15 Genotyping test, useful for optimizing therapy with thiopurine drugs (azathioprine, mercaptopurine, and thioguanine).
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