David Gerfast, a 12-year-old from Minnesota, is being treated at Boston's Massachusetts General Hospital for extraosseous chordoma, a rare form of cancer that is difficult to treat and attacks the bones.
The cancer was discovered in September after David was injured in a football game.
Thousands of miles from home, this Robin Young story is about how a family is fighting cancer with an old-fashioned ship captain's bell and high-tech proton beam radiation.
From the start of David's treatment in February
David on how he discovered the tumor
"I snapped the ball [in the football game] and somebody grabbed my facemask and I hurt my back and then got an MRI. And then they found the tumor."
David on his treatment
"I have treatment for eight weeks and then I'll get MRIs every three to six months. That's pretty much all I know about what's going to happen. I mean, I'm being as positive as I possibly can. It's hard without my mom and my sisters here, but my dad and I are getting through it."
Lars on his son
"He's very strong. Throughout this whole thing he's been very, very strong. But he has his moments where he breaks down. This is going to be a long process. These chordoma cells, they will come back, and he'll have to watch it his whole life."
David on the bell ringing tradition at MGH
"The last day of your treatment, you get to ring the bell. ... It will make me feel really good inside that I was able to beat this and go home."
Before David's final treatment in April
Cindy on being in Minnesota throughout most of her son's treatment
"It's terrible. I mean we have two younger daughters, 9 and 4, and pets and it's just such a huge support system back at home, but they're not here. So it was just dad and David having to pull the weight there, and then I pulled the weight at home with the girls. Thank goodness for Skype, but it's not the same."
Cindy on what she heard from the nurses about her son
"He has been a help to all these other little guys like Mack. And he would play trains and trucks with them every morning. And he would always want David: 'David, where's David?' And so they came back for Mack's, ringing of his bell, too."
Cindy on losing her mom to cancer
"I lost my mom to cancer when I was 12. And her anniversary of her death was Oct. 27, and that was the day we were supposed to meet with the surgeon the first time to hear his results. And I had told him when they did the biopsy, I said, 'If you're gonna tell me my son has cancer on the day my mom died from it, I can't hear it.' So they called us that Friday before on the 24th. And he's going to beat it. He's gonna win. He's gonna win."
Cindy on the bell-ringing ceremony
"It's just a completion. It's feeling this sense of, '[sigh], I made it. I'm done.' And there's a really nice little poem written over by the bell that really kind of says it all: 'I've conquered this moment.' "
After David's final treatment
David on ringing the bell
"It's hard to explain. It's just amazing. It felt like the biggest accomplishment I could have had."
This segment aired on May 26, 2015.