In July, 9-year-old Stephen Mondek became the youngest-known stem cell donor at Cedars-Sinai Medical Center when he donated stem cells to his father, Nick Mondek, MD, in an effort to treat his father’s leukemia. The procedure took place after Nick Mondek’s cancer returned earlier this year following a previous remission.
“A donation from a child this young is very rare,” said Hoyoung Chung, DO, a critical care pediatrician at Cedars-Sinai Guerin Children’s. “Stephen was very brave, and our team made sure everything went perfectly so that this young boy could help his father.”
Nick Mondek, an anesthesiologist working in Los Angeles, was diagnosed with acute myeloid leukemia in 2022. After initially receiving a transplant from his brother that led to remission, the disease recurred in April. Doctors sought another donor but were unable to find a match among relatives or through the National Bone Marrow Registry.
“We followed every clinical protocol but the disease still managed to come back, so we had a new problem on our hands,” said Ronald Paquette, MD, clinical director of the Stem Cell and Bone Marrow Transplant Program at Cedars-Sinai Cancer. “How could we treat his cancer a second time around and have a better chance that it doesn’t return?”
Mondek asked whether his son Stephen could be considered as a donor. Paquette confirmed that Stephen could be tested for compatibility since children inherit half their DNA from each parent and may serve as half-matched donors.
“The conversation with Stephen was pretty simple,” Mondek said. “I said, ‘Hey, Buddy, Dad’s sick and they need someone to give me stem cells, and they want to know if you want to get tested to see if you can do it.’”
Stephen responded: “When do we go?”
After tests showed compatibility and an evaluation confirmed Stephen understood the procedure and agreed to participate voluntarily, he underwent several weeks of preparation before being admitted for donation under general anesthesia. The process involved inserting a catheter into his neck vein and collecting stem cells over six hours.
“Being an anesthesiologist, I put people to sleep every day, so I reassured myself that everyone wakes up when they go to sleep under anesthesia,” Mondek said. “But during the whole process that I’ve gone through, those 60 minutes when Stephen was asleep were probably the toughest.”
The collection was successful; Stephen’s stem cells were frozen for later use.
A week later Nick Mondek began chemotherapy at Cedars-Sinai before receiving the transplant of his son’s stem cells.
“Transplant day is always dramatic,” Paquette said. “The patient knows that they cannot survive without the stem cells, and the delivery of the stem cells into their body is like a rebirth. We call that day their stem cell birthday.”
Following two weeks in hospital isolation while waiting for engraftment of new immune cells from Stephen’s donation—and missing family time—Mondek was discharged on August 16 and attended part of Stephen’s Little League game.
“I felt good helping my dad,” Stephen said, “and it felt good to have him home.”
Paquette noted it may take over a year before knowing if this treatment will result in long-term remission but described both father and son as determined not to accept anything less than success.
John Chute MD commented on Cedars-Sinai’s approach: “Our exceptional patient care is part of the reason that our stem cell transplantation program has enjoyed consecutive top 10 national rankings by the Center for International Blood and Marrow Transplant Registry (CIBMTR) for patient outcomes since 2021,” Chute said.
Mondek expressed optimism about his prognosis: “Everything lined up for this,” he stated. “Dr. Paquette said the perfect donor for me would be someone who’s young and healthy and a 50% match, and we found him. He was right here in front of us.”
Cedars-Sinai Medical Center is located in Los Angeles and has operated since 1902 under current president Thomas M. Priselac; it serves as both a major hospital—with more than 50 thousand annual admissions according to its most recent report—and as an academic institution with specialized pediatric services.
