Northern Colorado girl becomes first-known childhood brain stem cancer survivor, example to future cases

For most children, kicking a soccer ball around the backyard is an everyday activity. For 6-year-old Hadley McMahon, it's something her Colorado family once feared they would never see.

Hadley, a Frederick resident, is now cancer-free after surviving an extraordinarily rare and aggressive brain stem cancer that was discovered when she was only a few months old. Diagnosed with an infant high-grade glioma, a rare and aggressive brain tumor, Hadley was treated by the Center for Cancer and Blood Disorders at Children's Hospital Colorado.

The genetics of Hadley's tumor were entirely unique, placing her among only a small number of patients worldwide diagnosed with the condition in the brainstem. Her case was only the second of its kind ever treated at Children's Hospital Colorado.

"Everything was against all odds," said Amber McMahon, her mother.

When doctors first identified the tumor on Hadley's brainstem, the outlook was devastating. The tumor's location made surgery challenging and its aggressive nature left few established treatment options. Doctors and Hadley's family were entering largely uncharted territory.

Because of the tumor's location and the lack of previous treatment cases, her care team could not offer a clear roadmap for what would come next.

"You should hold no hope. This will beat her," McMahon recalled being told.

Dr. Nathan Dahl, a physician at Children's Hospital Colorado who helped oversee Hadley's care, said the difficult prognosis reflected what medical experts knew at the time.

"All the signs that we had pointed to this being really, really, really grim," Dahl said. "It's something that there's been maybe a handful of cases reported worldwide ever."

Hadley was not expected to survive infancy. Faced with a diagnosis that often leads families to forgo treatment, the McMahons chose to move forward.

"She had a brain biopsy, chemo," McMahon said.

What followed was a remarkable turnaround. Through advanced genetic sequencing, chemotherapy and the expertise of a large medical team, doctors were able to identify a treatment approach tailored to Hadley's unique tumor. With the help of precision medicine and months of treatment, Hadley began defying expectations.

"At the two-year mark, they said, 'We think we might have cured her,'" McMahon said. "At the five-year mark she rang the bell, and she's cured."

Today, Hadley spends her time doing what many children her age enjoy. She loves going to school, playing sports and video games with her older brother and looking forward to new adventures.

"To have her cured and start kindergarten and be a little girl and go on vacations, you know, it was a big shift," McMahon said. "It's amazing."

Beyond her own recovery, Hadley's case is helping reshape expectations for future patients diagnosed with similar cancers.

"The next family won't be told (to not have hope)," McMahon said. "They'll be told, 'We might have an answer.'"

For Dahl and the medical team at Children's Hospital Colorado, Hadley's story represents the progress being made through research, genetic testing and personalized treatment. For her family, it represents something even more meaningful: a future they once thought was impossible.

Hadley understands that her experience could help other children facing the same battle.

"(I am) happy, because they get to live the life that I do," Hadley said.

Her mother, Amber, said she never imagined their cancer journey would lead to a hopeful chapter.

"I never envisioned a rewarding chapter to a cancer journey," Amber McMahon said. "The one that we were having was supposed to be very traumatic for us, and instead now she's raising hundreds of thousands of dollars for kids like her, facing things like she is."

Years after doctors feared the worst, Hadley is thriving, serving as a living example of how medical innovation, determined caregivers and a family's refusal to give up can sometimes overcome even the longest odds.