Her music career seemed to be taking off, but then Jax was diagnosed with thyroid cancer. The 20-year-old New Yorker is using running to overcome it and keep her on a healthy track. Her next challenge? This year’s New York City Marathon.

Jax’s life has been a whirlwind since her third-place finish on season 14 of American Idol in 2015, and the release of her first two singles, with more on the way. But the characteristically bubbly 20-year-old singer—born Jaclyn Miskanic—was feeling down and lethargic during an American Idol tour last spring. She chalked it up to the rigors of life on the road.

Instead, doctors found 18 tumors on her thyroid—12 of them cancerous. The diagnosis was all the more terrifying because there was a family history. Surgery was the best treatment for Jax but her grandfather recently lost his voice after a similar procedure. That’s a scary prospect for a young professional singer, especially one who was just starting to establish herself.

“I was totally MIA for like two months when I first found out about and was dealing with my cancer,” JAX says by phone from Nashville, where she’s working on some new songs. “Now I almost feel guilty. That’s why I decided I needed to share my story.”

Jax credits her mom, Jill, a schoolteacher in New York, with going into “FBI-investigator mode” to find the best possible surgeon and team. Her research worked: Jax is currently recovering—and still receives radiation treatments. Her powerful voice is intact, although some say it’s slightly raspier. But Jax, who counts Janis Joplin as one of her idols, doesn’t mind that. 

And one thing that’s helped her deal with her diagnosis and treatment for thyroid cancer is running. In fact, she plans to run the New York City Marathon on Nov. 6 for the charity group Tuesday’s Children, an organization that supports youth affected by terrorism.

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Born in East Brunswick, N.J., and a New Yorker since the age of 12, she says the city is her hometown. Her parents both grew up in Brooklyn, and her father, a retired firefighter, was a first responder on September 11, 2001. She knows that running the city’s signature race is a big moment.

“It’s a statement for me to say I’m the healthiest I can possibly be and that I’m feeling strong,” Jax says. “I also want to show others who may be dealing with cancer that there’s hope and you can get through it.”

Though she keeps a busy schedule, Jax normally runs 6 to 8 miles a day, even while touring, then a long run once a week. (She just ran her first 14-miler.)

“I feel the healthiest when I’m in a workout regimen,” she says. “Thyroid issues in general mess with your immune system, and my immune system has always been wacky. Running, especially training, is keeping me on track and motivated. Running has always been really therapeutic for me. If I’m stressed or going through something tough, you can tell because I’ll be ripped!”

As for Jax’s running habits, this singer who’s been around music her whole life actually listens to music only sometimes on the run. And she sees unlikely similarities in her two passions.

“Music pumps me up,” she says. “But when I have good scenery, I don’t listen to music. I like to hear what’s around me. I’m definitely in a creative state when I run. There are times when the run is almost over and I feel like I just started. It’s inspirational and good free space for my brain. For me, working in the studio, writing and creating is just as cathartic as running. They go hand in hand as far as being able to relax and sort my mind.”

But she probably couldn’t take all this on without the help of others. She hates running on treadmills and prefers to run outside. But in light of the recent fatal attacks on runners in New York, she runs with someone when she runs at night.

Then there are also Jax’s fans. Even with a couple of singles, “Forcefield” and “La La Land” to her name, she feels that she didn’t have as much of a voice or spotlight before cancer.

“I sill keep in touch with a girl I met in Texas while I was on tour,” Jax says. “She’s 5 and has had cancer her whole life. But she reached out to thank me for sharing. It’s really nice. Especially knowing some will be out during the marathon too!”

One particular fan she hopes to see at the finish line is her 18-year-old brother, Matt, with whom she’s close, and who recently finished Marine Corps boot camp.

“He still needs to remember who’s boss!” Jax says. “But seeing him at the finish line would be a great motivator for me.”

And finally there are all the people she’s running with on behalf of Tuesday’s Children. (Jax says a related organization, Families of Freedom Scholarship Fund, helped put her and her brother through school.)

“It’s cool to be part of a team,” she says. “I know that I’m training with people even if we aren’t actually running together. It’s definitely a motivating factor. We’ll all have a pasta dinner and a post-race party when we’re in New York. It’s going to be great!”

In her first marathon, she’s not running for time, of course—her goal is simply to get to the finish line in her bright orange Nike Air Zoom Pegasus 33’s and enjoy herself. Until then, this busy pop star will continue to be on the move and hard at work, with an appropriately pop-star buildup to the race: She’ll be releasing a new single in time for the marathon.

You can help! To donate for Jax’s charity connected to her run, go to Crowdrise.com/jaxpack.