JoEllen Zembruski-Ruple, while in the care of New York City鈥檚 renowned Memorial Sloan Kettering Cancer Center, swallowed the first three chemotherapy pills to treat her squamous cell carcinoma on Jan. 29, her family members said. They didn鈥檛 realize the drug could kill her.
Six days later, Zembruski-Ruple went to Sloan Kettering鈥檚 urgent care department to treat sores in her mouth and swelling around her eyes. The hospital diagnosed oral yeast infection and sent her home, her sister and partner said. Two days later, they said, she returned in agony 鈥 with severe diarrhea and vomiting 鈥 and was admitted. 鈥淓nzyme deficiency,鈥 Zembruski-Ruple texted a friend.
The 65-year-old, a patient advocate who had worked for the National Multiple Sclerosis Society and other groups, would never go home.
Covered in bruises and unable to swallow or talk, she eventually entered hospice care and from the very drug that was supposed to extend her life, said her longtime partner, Richard Khavkine. Zembruski-Ruple was deficient in the enzyme that metabolizes capecitabine, the chemotherapy drug she took, said Khavkine and Susan Zembruski, one of her sisters. Zembruski-Ruple was among or its cousin, the IV drug fluorouracil known as 5-FU.

Doctors can test for the deficiency 鈥 and then if patients have a genetic variant that carries risk. The FDA , but it鈥檚 expensive and must be administered within four days of the first chemotherapy treatment.
Newer cancer drugs sometimes include a companion diagnostic to determine whether a drug works with an individual patient鈥檚 genetics. But 5-FU went on the market in 1962 and sells for about $17 a dose; producers of its generic aren鈥檛 seeking approval for toxicity tests, which typically cost hundreds of dollars. Doctors have only gradually understood which gene variants are dangerous in which patients, and how to deal with them, said Alan Venook, a colorectal and liver cancer specialist at the University of California-San Francisco.
By the time Zembruski-Ruple鈥檚 doctors told her she had the deficiency, she had been on the drug for eight days, said Khavkine, who watched over his partner with her sister throughout the seven-week ordeal.
Khavkine said he 鈥渨ould have asked for the test鈥 if he had known about it, but added 鈥渘obody told us about the possibility of this deficiency.鈥 Zembruski-Ruple鈥檚 sister also said she wasn鈥檛 warned about the fatal risks of the chemo, or told about the test.
鈥淭hey never said why they didn鈥檛 test her,鈥 Zembruski said. 鈥淚f the test existed, they should have said there is a test. If they said, 鈥業nsurance won鈥檛 cover it,鈥 I would have said, 鈥楬ere鈥檚 my credit card.鈥 We should have known about it.鈥
Guidance Moves at a Glacial Pace
Despite growing awareness of the deficiency, and an advocacy group made up of grieving friends and relatives of all patients before they take the drug, the medical establishment has moved slowly.
A panel of the National Comprehensive Cancer Network, or NCCN 鈥 specialists from Sloan Kettering and other top research centers 鈥 until recently did not recommend testing, and the FDA does not require it.
In response to a query from 黑料吃瓜网 News about its policy, Sloan Kettering spokesperson Courtney Nowak said the hospital treats patients 鈥渋n accordance with NCCN guidelines.鈥 She said the hospital would not discuss a patient鈥檚 care.
On Jan. 24, the FDA about the enzyme deficiency in which it urged health care providers to 鈥渋nform patients prior to treatment鈥 about the risks of taking 5-FU and capecitabine.
On March 31 鈥 six days after Zembruski-Ruple鈥檚 death 鈥 the network鈥檚 expert panel for most gastrointestinal cancers took a first step toward recommending testing for the deficiency.
Worried that President Donald Trump鈥檚 FDA might do nothing, Venook said, the panel 鈥 whose guidance shapes the practices of oncologists and health insurers 鈥 recommended that doctors consider testing before dosing patients with 5-FU or capecitabine.
However, its guidance stated that 鈥渘o specific test is recommended at this time,鈥 citing a lack of data to 鈥渋nform dose adjustments.鈥
Sloan Kettering 鈥渨ill consider this guidance in developing personalized treatment plans for each patient,鈥 Nowak told 黑料吃瓜网 News.
The new NCCN guidance was 鈥渘ot the blanket recommendation we were working toward, but it is a major step toward our ultimate goal,鈥 said Kerin Milesky, a public health official in Brewster, Massachusetts, who鈥檚 part of an advocacy group for testing. Her husband, Larry, died two years ago at age 73 after a single treatment of capecitabine.
began urging oncologists to test patients for deficiency in May 2020. Patients with potentially risky genetics are started on a half-dose of the cancer drug. If they suffer no major toxicity, the dose is increased.
A Lifesaving Ultimatum?
Emily Alimonti, a 42-year-old biotech salesperson in upstate New York, chose that path before starting capecitabine treatment in December. She said her doctors 鈥 including an oncologist at Sloan Kettering 鈥 told her they didn鈥檛 do deficiency testing, but Alimonti insisted. 鈥淣ope,鈥 she said. 鈥淚鈥檓 not starting it until I get the test back.鈥
The test showed that Alimonti had a copy of a risky gene variant, so doctors gave her a lower dose of the drug. Even that has been hard to tolerate; she鈥檚 had to skip doses because of low white blood cell counts, Alimonti said. She still doesn鈥檛 know whether her insurer will cover the test.

Around 300,000 people are treated with 5-FU or capecitabine in the United States each year, but its toxicity could well have prevented FDA approval were it up for approval today. Short of withdrawing a drug, however, U.S. regulators have little power to manage its use. And 5-FU and capecitabine are still powerful tools against many cancers.
At a January workshop that included FDA officials and cancer specialists, Venook, the NCCN panel鈥檚 co-chair, asked whether it was reasonable to recommend that doctors obtain a genetic test 鈥渨ithout saying what to do with the result.鈥
But Richard Pazdur, the FDA鈥檚 top cancer expert, said it was time to end the debate and commence testing, even if the results could be ambiguous. 鈥淚f you don鈥檛 have the information, how do you have counseling?鈥 he asked.
Two months later, Venook鈥檚 panel changed course. The price of tests has fallen below $300 and results can be returned as soon as three days, Venook said. Doubts about the FDA鈥檚 ability to further confront the issue spurred the panel鈥檚 change of heart, he said.
鈥淚 don鈥檛 know if FDA is going to exist tomorrow,鈥 Venook told 黑料吃瓜网 News. 鈥淭hey鈥檙e taking a wrecking ball to common sense, and that鈥檚 one of the reasons we felt we had to go forward.鈥
On May 20, the FDA posted a seeking public input on the issue, a move that suggested it was considering further action.
Venook said he often tests his own patients, but the results can be fuzzy. If the test finds two copies of certain dangerous gene variants in a patient, he avoids using the drug. But such cases are rare 鈥 and Zembruski-Ruple was one of them, according to her sister and Khavkine.
Many more patients have a single copy of a suspect gene, an ambiguous result that requires clinical judgment to assess, Venook said.
A full-gene scan would provide more information but adds expense and time, and even then the answer may be murky, Venook said. He worries that starting patients on lower doses could mean fewer cures, especially for newly diagnosed colon cancer patients.
Power Should Rest With Patients
Scott Kapoor, a Toronto-area emergency room physician whose brother Anil, a much-loved urologist and surgeon, died of 5-FU toxicity at age 58 in 2023, views Venook鈥檚 arguments as medical paternalism. Patients should decide whether to test and what to do with the results, he said.
鈥淲hat鈥檚 better 鈥 don鈥檛 tell the patient about the test, don鈥檛 test them, potentially kill them in 20 days?鈥 he said. 鈥淥r tell them about the testing while warning that potentially the cancer will kill them in a year?鈥
鈥淧eople say oncologists don鈥檛 know what to do with the information,鈥 said Karen Merritt, whose mother died after an infusion of 5-FU in 2014. 鈥淲ell, I鈥檓 not a doctor, but I can understand the Mayo Clinic report on it.鈥
The Mayo Clinic recommends starting patients on half a dose if they have one suspect gene variant. And 鈥渢he vast majority of patients will be able to start treatment without delays,鈥 Daniel Hertz, a clinical pharmacologist from the University of Michigan, said .
Some hospitals began testing after patients died because of the deficiency, said Lindsay Murray, of Andover, Massachusetts, who has advocated for widespread testing since her mother was treated with capecitabine and died in 2021.
In some cases, Venook said, relatives of dead patients have sued hospitals, leading to settlements.
Kapoor said his brother 鈥 like many patients of non-European origin 鈥 had a gene variant that hasn鈥檛 been widely studied and isn鈥檛 included in most tests. But a full-gene scan would have detected it, Kapoor said, and such scans can also be done for a few hundred dollars.
The cancer network panel鈥檚 changed language is disappointing, he said, though 鈥渂etter than nothing.鈥
In to Zembruski-Ruple, her friends, colleagues, and clients remembered her as kind, helpful, and engaging. 鈥淛oEllen was beautiful both inside and out,鈥 said Barbara McKeon, a former colleague at the MS Society. 鈥淪he was funny, creative, had a great sense of style.鈥
鈥淛oEllen had this balance of classy and playful misbehavior,鈥 psychotherapist Anastatia Fabris said. 鈥淢y beautiful, vibrant, funny, and loving friend JoEllen.鈥