Why Don’t U.S. Guidelines Recommend DPYD Testing Before Chemotherapy? Cancer Patients Are Dying To Know.

One in 20 people carries one change in a gene called DPYD. If they do, they likely don’t know it – but if they develop cancer and are given certain types of chemotherapy (fluorouracil (5-FU) or capecitabine (Xeloda or CAPE), they may get very sick or die. In the United States alone it is estimated that 700-1,400 patients die of 5-FU toxicity yearly.

Karen Merritt knows about DPYD too well. Her mom was diagnosed with anal cancer at age 73 and was treated with 5-FU. First, she developed continuous diarrhea and sores in her mouth. Next, she became dehydrated and collapsed. Then she was taken to the hospital and within a month she was dead – not from the cancer, but from the treatment that was supposed to help her. Why? She carried a DPYD mutation and didn’t know it. Such toxicity was suspected in the emergency room and written in her chart. But toxicity to 5-FU was not listed as her cause of death (cardiac arrest was) and her case was not reported to the FDA as an adverse drug event, hindering data collection on how often these deaths occur.

Her mom’s death led Karen to co-found Advocates for Universal DPD/DPYD Testing. This group wants the United States to follow the lead of the EU, UK, most of Canada, Australia, and Zimbabwe in recommending that all patients undergo DPYD testing before they are given 5-FU. DPYD testing costs roughly $300, as compared to the hundreds of thousands of dollars that chemotherapy costs. The cost of treating someone who develops DPYD-toxicity can exceed $180,000, is traumatic, and may not be successful. DPYD testing is done using a single tube of blood or a cheek swab and results are generally available within 7 days. It can reduce overall costs to our medical system.

Why is the United States the last Western country that is not recommending DPYD testing before administering chemotherapy? Dr. John Strickler, a medical oncologist at DukeHealth, says that pharmacogenetic testing is more complicated and nuanced than it first appears. Some clinicians recommend testing for a large panel of genes related to drug responses. However, there is wide variability in how well the results predict drug toxicity. Performing genetic testing can delay the initiation of chemotherapy for some patients (although this should not be an issue if the test is ordered shortly after diagnosis). Furthermore, not all insurance companies cover the testing.

These are valid points, but Dr. Strickler acknowledged that at Duke they now have universal testing for DPYD before 5-FU or Capecitabine are administered. I inquired why his colleagues on the NCCN colon, rectal, and anal panels (even those at centers, like Duke, that require testing at their own institutions) have voted against universal recommendations for DPYD testing. Strickler explained that these panels are conservative about adopting change, but that the whole country is now moving in the direction of universal DPYD testing.

During his medical training Dr. Dan Flora saw a patient who died of 5-FU toxicity and he never forgot him. As a medical oncologist who also has a degree in pharmacology, Dr. Flora’s driving principle is “how do we keep patients safe?”. He works at St. Elizabeth Healthcare in Kentucky, a progressive community cancer center that has developed ‘an easy button’ for pharmacogenetics testing, including DPYD, showing that it can be done. “It is automated now. We have built it into our electronic medical record and it pops up before we can prescribe these chemotherapy drugs.”

What needs to happen for DPYD testing before chemotherapy to be the standard of care in the United States? “Changing NCCN recommendations to include this testing would transform the United States overnight”, says Dr. Scott Kapoor, whose brother, world-renowned academic urologist, uro-oncologist and renal transplant surgeon, Dr. Anil Kapoor died at age 58 from DPYD-related toxicity. Dr. Kapoor carried at least one deleterious variant in the DPYD gene. “Oncologists, the courts and insurance companies in the U.S. look to the NCCN to set the standard of care.”

Dr. Strickler suggested a parallel approach. “If insurance companies refused to pay for this chemotherapy until the patient had DPYD testing, universal testing would be adopted immediately.” Perhaps it is time for both approaches to occur, in unison.

Three decades of data on DPYD are no longer ambiguous and the liability for health systems should serve as an added incentive for national guidelines to recommend universal DPYD testing, and for health systems to adopt these policies, now. Your cancer patients and their families deserve it, and their lives may depend on it.

This is the 2nd article by Matloff on DPYD testing. Read the first here.

Many thanks to Beth N. Peshkin, MS, CGC for her invaluable review and edits.