JoEllen Zembruski-Ruple, while in the care of New York City's 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't realize the drug could kill her.

Six days later, Zembruski-Ruple went to Sloan Kettering's 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 -- with severe diarrhea and vomiting -- and was admitted. "Enzyme deficiency," Zembruski-Ruple texted a friend.

The 65-year-old, a patient advocate who had worked for the National Multiple Sclerosis (MS) Society and other groups, would never g

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