Dad Facing ‘Aggressive’ Cancer Thought This Christmas Could Be His Last—Son’s Stem Cell Donation Offers Lifesaving Hope

“I felt good helping my dad,” 9-year-old Stephen Mondek said, reflecting on the extraordinary gift that may have saved his father’s life.

Dr. Nick Mondek, an anesthesiologist from Los Angeles, believes that this upcoming Christmas could have been his last—if not for his young son’s intervention during a harrowing battle with acute myeloid leukemia.

In July, Stephen became the youngest-known stem cell donor at a Los Angeles children’s hospital, offering a lifeline to his father. Nick had already undergone a stem cell transplant from his older brother, Dave, but after two and a half years of remission, the cancer returned with a vengeance.

“It’s just amazing,” Nick, 48, said, describing his son’s selfless act. “I got a second chance at a second chance, just to still be here. Without that transplant, things would not be good right now.”

The journey began in the spring of 2022, when Nick started feeling unusually unwell for about a month. The diagnosis of a rare blood cancer that attacks the bone marrow was life-altering, he recalls. Nick and his wife, Danielle Boyer, share Stephen, now 10, and their younger son, John, 6.

Dave’s initial stem cell donation had successfully brought Nick back to health, creating what he describes as an internal “army” to fight the cancer. But even then, the threat of recurrence loomed.

“I had a feeling that it would come back. I just didn’t know when,” Nick explained. “It’s a very aggressive disease, and I had a few mutations that make it even more difficult to treat and more prone to relapse.”

By 2025, more than two years after his first transplant, the leukemia returned with ferocity. Nick faced the frightening reality of a second battle—but this time, his young son’s heroic donation gave him renewed hope and, quite literally, a second chance at life.

“We followed every clinical protocol, but the disease still managed to come back, leaving us with a new and urgent challenge,” said Dr. Ronald Paquette, clinical director of the Stem Cell and Bone Marrow Transplant Program at Cedars-Sinai Cancer. “The question became: how could we treat his cancer a second time and improve the chances that it wouldn’t return?”

Nick Mondek’s care team faced a daunting obstacle: finding another compatible donor. Stem cells from his two older brothers were no longer viable, and the National Bone Marrow Registry, as well as other family members, offered no feasible options.

The reality of his situation hit Nick hardest while he was waiting for an appointment with his doctor. “I’m not ready to leave them yet,” he thought, thinking of his young children.

A spark of hope came from a friend whose 18-year-old son had donated stem cells to help a family member battling lymphoma. Nick asked his doctor whether a child could meet the age and size requirements to donate. When the doctor confirmed that his eldest son, Stephen, might be a suitable donor, Nick began a careful conversation with his family.

“I didn’t want him to feel obligated or pressured,” Nick recalled. “I didn’t even tell him that he was essentially our last hope.”

Instead, he framed it gently, telling Stephen they were exploring potential donors. “We’re wondering if you’d like to be tested to see if you might want to help,” he asked, giving his son the choice without pressure.

Stephen’s response was immediate: “Yeah, let’s do it.”

Once the then 9-year-old was confirmed as a match, the team at Cedars-Sinai Guerin Children’s Pediatrics ensured Stephen fully understood the procedure he was about to undergo. Over the following weeks, he completed a series of “pre-donation prep” steps designed to ready his body for the stem cell collection.

On the day of the donation, Stephen was placed under general anesthesia so doctors could insert a catheter into a vein in his neck. In the Intensive Care Unit, his blood was circulated through a centrifuge that extracted the stem cells needed for the transplant, a process that took roughly six hours, according to the hospital.

“That hour while he was asleep under anesthesia was probably one of the toughest periods of my life,” Nick recalls. “You start to question everything—am I doing the right thing?”

Fortunately, the procedure went smoothly, and Stephen was able to return home that same evening. Nick’s part of the process followed shortly after: six days of chemotherapy to prepare his body, followed by the long-awaited stem cell transplant.

“Transplant day is always dramatic,” said Dr. Ronald Paquette, clinical director at Cedars-Sinai, describing the moment when stem cells are delivered into the patient’s body. “The patient knows they cannot survive without the stem cells, and that delivery is like a rebirth. We call that day their stem cell birthday.”

Nick remained hospitalized for two weeks after the procedure as his immune system slowly recovered. By August 16, he was well enough to attend one of Stephen’s Little League games—a simple yet profound milestone for the father who credits his son with giving him a renewed chance at life.

“I just hope he knows what his actions can do in life, just helping another person,” Nick said. “It’s an amazing feeling.”

For Stephen, the experience was equally meaningful. “I felt good helping my dad,” he said. “It felt good to have him home.”

Paquette noted that it could take more than a year to determine whether Nick’s new immune system will successfully fight off the leukemia. Still, the Mondeks remain cautiously optimistic.

“I’m just glad that I still get to be around and watch them grow up,” Nick said, looking forward to taking his sons to see the Cubs play at Wrigley Field in Chicago.

“I’m a simple guy,” he added. “I don’t need to climb Kilimanjaro or swim the English Channel to celebrate. I just want to be with my family and enjoy whatever time I have.”