For the first time in her life, 7-year-old Erin Cross was healthy enough to go trick-or-treating.

This Halloween marked a monumental milestone for 7-year-old Erin Cross. For the first time in Erin’s life, she was healthy enough to go trick-or-treating. And her costume of choice – an old woman – held a special meaning for her family.

Two years ago, Erin’s family was facing the devastating reality that they may never see her grow up. But today, she’s in remission thanks to a groundbreaking immunotherapy clinical trial at Seattle Children’s. Her family finally has the chance to envision her long life ahead, a life filled with normal things, like trick-or-treating and playing with other kids.

“Erin has been so incredibly brave,” said her mother, Sarah Cross. “For us, normal was being in the hospital. Today, she’s cancer-free and getting back to normal life.”

A long journey, a bright future

At age 2, Erin was diagnosed with acute lymphoblastic leukemia (ALL), a cancer of the white blood cells. Initial cancer treatments put Erin into remission, but in 2016, Erin’s family received the heartbreaking news that she had relapsed.

They had exhausted every treatment option available near their hometown of Chester, England. After extensive research, Sarah found Seattle Children’s Pediatric Leukemia Adoptive Therapy (PLAT-02) clinical trial for children and young adults with relapsed or refractory ALL who are not likely to survive with current treatments. As their last hope, the family contacted Seattle Children’s and applied for the clinical trial.

Erin Cross, 7, flew from England to receive treatment for ALL at Seattle Children’s.

The PLAT-02 chimeric antigen receptor (CAR) T-cell immunotherapy trial harnesses a patient’s own immune system to seek and destroy cancer. After seeing promising results in phase 1 of the trial with 93% of patients achieving complete initial remission, researchers at Seattle Children’s embarked on a quest to reduce the rate of relapse following the experimental therapy, which is about 50%. Today, that quest is moving forward. Seattle Children’s has continued to improve the therapy and is opening PLAT-05, the first CAR T-cell trial in the U.S. for children and young adults to target two separate proteins expressed by some leukemia cells simultaneously.

“Seattle Children’s threw us a lifeline,” said Sarah. “We knew we had to get her there. We moved mountains to get Erin to Seattle.”

In July 2016, Erin’s family arrived in Seattle for the trial. According to Erin’s parents, they immediately felt at home.

“It wasn’t a coincidence we found Seattle Children’s,” said Antony, Erin’s dad. “As soon as we walked into the hospital, we knew it was the place we were supposed to be.”

Upon meeting Dr. Rebecca Gardner, Seattle Children’s oncologist and the lead investigator of the PLAT-02 and PLAT-05 trials, the family wasted no time with words. They gave Gardner a big hug.

“We had confidence the treatment would work,” said Sarah. “Dr. Gardner looked after us at a time when we were really vulnerable.”

Harnessing Erin’s immune system

Erin’s T cells were reprogrammed to seek out and destroy cancer cells.

In August, Erin’s T cells were reprogrammed to be able to seek and destroy cancer cells wherever they were hiding in her body. A few weeks later, they were reinfused back into her body to fight the cancer cells, similar to how a person’s immune system fights a virus.

The family waited for news as Erin’s T cells attacked the cancer cells. On Sept. 21, 2016, the family received a phone call from Gardner.

“I still remember that morning really well,” said Antony. “Sarah and I were quite apprehensive to hear the results. Erin and I were playing when the phone went off. I could see it was from Seattle Children’s. I knew Sarah wanted to take the call, so against every instinct in my body, I let it go.”

Minutes later, Sarah came walking into the room, tears in her eyes.

“We knew they would either tell us there was no more hope, or that she’d have a chance at a normal life,” said Sarah.

One question plagued their minds: did the therapy work?

The voice on the other end had a simple and life-altering answer: Yes.

“We cried for quite a long time that day,” said Sarah. “They were tears of relief.”

There was no detectable cancer. Erin was in remission.

Erin captured Prince Harry’s heart at the WellChild Awards.

Going viral

A year later, Erin is still in remission and enjoying life. According to her mother, “She’s the life of the party.”

Erin was recently recognized for her bravery, and had the honor of being selected among hundreds of nominations as a winner of the prestigious 2017 WellChild Awards in London. As a part of the award, she even got to meet Prince Harry, more than once.

“She’s met him five times,” said Sarah. “Erin likes to say she’s met him more than his girlfriend.”

Erin made more international headlines the day after the WellChild award ceremony. During a live interview with ITV News, a television station in England, she asked the reporter a poignant question. “Are you single?” She was asking for a friend.

“She captured the heart of the nation with that question,” said Antony. “She’s such a character. It should have been no surprise. It was a very Erin thing to ask.”

Getting back to normal life

More than anything, Erin’s family is looking forward to her future.

“We want her to have a normal life,” said Sarah.

Attending school full time and playing with friends wasn’t possible before, but now that Erin is doing so well, she’s ready to get back to doing things children her age do.

“Erin is craving normality,” said Antony. “She’s been isolated for quite a while. She’s spent so much time with us, I’m sure she wants to be around other children.”

Advancing treatment options

The Cross family hopes to visit Seattle again. Sarah says she can’t thank the hospital enough for what they’ve done for Erin.

“We miss everyone terribly,” said Sarah. “Seattle is our second home. We’ve been homesick.”