It felt like a miracle.

The worst day of Sarah and Antony Cross’ life was when they found out their 2-year-old daughter, Erin, had leukemia.

“Erin endured years of chemotherapy, and we thought we had the cancer beat,” said Erin’s mother, Sarah. “She blossomed into a beautiful, healthy girl. She was doing really well at school, making friends, just being a normal kid.”

But 11 months after her treatment ended, a routine blood test showed something abnormal. The world fell apart all over again when they heard the news that Erin’s cancer was back.

She battled through more cycles of chemotherapy, but at week five, they received crushing news. Erin wasn’t responding to the chemo as well as she should. This meant even more treatment. More hospital stays. More sickness.

And weeks later, when the tests came back, they showed the cancer was still there.

Just a few years ago, Erin would have been out of options. However, thanks to the generosity of donors like you, Seattle Children’s has had success with a new treatment called immunotherapy.

Immunotherapy “reprograms” a child’s own T cells (the white blood cells that fight infection) to hunt down and destroy cancer cells,-reducing the need for chemotherapy and radiation and their often-lifelong side effects.

Immunotherapy treatment is already showing amazing results – 93% of patients with relapsed acute lymphoblastic leukemia, all of whom were out of hope, achieved remission using the power of their own immune systems.

The Cross family traveled more than 4,000 miles from their home in England to Seattle Children’s to participate in the trial. Doctors extracted some of Erin’s T cells from her blood, reprogrammed them over the course of a few weeks, and then put them back in her with a simple infusion.

“For us, that infusion – that one moment – meant everything,” said Erin’s father, Antony. “That one moment could give us back our little girl.”

The Cross family waited anxiously as the modified T cells went to work in Erin’s body. After a few weeks, they got the call they’d been dreaming of.

“It was so amazing to hear the words “no signs of leukemia,” said Sarah. “We had never had a negative test before. It felt like a miracle!”

The groundbreaking treatment that gave Sarah and Antony back their little girl, is only possible because of a dedicated team of researchers and donors, like you, who are working tirelessly to accelerate this research so more kids like Erin can have a healthy and bright future.

“It’s still hard to believe what we set out to achieve in Seattle has worked,” said Sarah. “Our little girl is cancer free, something we never thought would happen. Erin will be able to go back to school, see her friends and begin to lead the normal life that she’s never truly known.”