A quick test could protect against fatal chemo overdose, yet few cancer doctors use it
The chemotherapy drug 5-FU can be toxic to some people with cancer. A quick, cheap test can show if chemo is safe for a patient, but few doctors order it.
One January morning in 2021, Carol Rosen took a standard treatment for metastatic breast cancer. Three gruesome weeks later, she died in excruciating pain from the very drug meant to prolong her life.
Rosen, a 70-year-old retired schoolteacher, passed her final days in anguish, enduring severe diarrhea and nausea and terrible sores in her mouth that kept her from eating, drinking, and, eventually, speaking. Skin peeled off her body. Her kidneys and liver failed. “Your body burns from the inside out,” said Rosen’s daughter, Lindsay Murray, of Andover, Massachusetts.
Rosen was one of more than 275,000 cancer patients in the United States who are infused each year with fluorouracil, known as 5-FU, or, as in Rosen’s case, take a nearly identical drug in pill form called capecitabine. These common types of chemotherapy are no picnic for anyone, but for patients who are deficient in an enzyme that metabolizes the drugs, they can be torturous or deadly.
Carol Rosen, left, and her daughter, Lindsay Murray, celebrate Thanksgiving in 2020. Rosen, a 70-year-old retired schoolteacher, passed her final days in anguish after three weeks of chemotherapy with incompatible drugs. Justin Murray / KFF Health NewsThose patients essentially overdose because the drugs stay in the body for hours rather than being quickly metabolized and excreted. The drugs kill an estimated 1 in 1,000 patients who take them — hundreds each year — and severely sicken or hospitalize 1 in 50. Doctors can test for the deficiency and get results within a week — and then either switch drugs or lower the dosage if patients have a genetic variant that carries risk.
Yet a recent survey found that only 3% of U.S. oncologists routinely order the tests before dosing patients with 5-FU or capecitabine. That’s because the most widely followed U.S. cancer treatment guidelines — issued by the National Comprehensive Cancer Network — don’t recommend preemptive testing.
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