Sixteen years ago, Guido’s right leg hurt, but none of his doctors could figure out why. “I knew something was wrong, but nobody knew the reason. The worst thing was I didn’t know what to do about it,” says Guido, who was a college student in Austria at the time.

Tests didn’t show anything out of the ordinary, so he just had to live with the pain. But then, after nearly a year, it got so bad he was hospitalized—and this time X-rays revealed something growing around his thigh bone (femur). Genetic testing identified the growth as Ewing sarcoma, a rare cancer that usually affects children and adolescents. “It’s very uncommon in people in their 20s,” Guido says. “It’s not the first thing physicians think of.”

By the time he got his diagnosis, the cancer had spread to other bones, as well as to his marrow.

Because he had a so-called children’s disease, Guido was transferred to a children’s hospital with specialists in Ewing sarcoma. There, he enrolled in a clinical trial that entailed intensive chemotherapy. Although the mutation that causes Ewing sarcoma is known, this cancer still has no targeted treatment today.

Altogether, his treatment took 8 months. After a first round of chemotherapy to shrink the tumors, Guido had surgery on his femur to remove the primary tumor. This necessitated partial replacement of his hip and femur. Next came more chemotherapy, including a powerful high-dose round.

Guido withstood this difficult treatment partly with palliative care, including medicine to protect his digestive system, traditional Tibetan herbal medicine, and meditation. He also exercised as much as he could given that he was in a hip-to-ankle cast and on crutches. “All this helped with the side effects and my psychological state,” he says.

But exercise also made the final part of his treatment impossible. His doctors had planned to follow chemotherapy with radiation that targets rapidly growing tumor cells, but a scan showed his bones were riddled with metabolically active cells. “One of my doctors initially said it didn’t look good,” Guido says. “At the time I was very nervous.” Luckily, follow-up scans showed no signs of tumors, and he now attributes all those active bone cells to his exercise while hospitalized.

Childhood cancers are unlike most adult cancers, which often are chronic and manageable with treatment. In contrast, tumors in young people tend to grow very fast. This can make them either harder to control or easier to eradicate with treatments that target rapidly dividing cells. “Usually with children’s cancer, you are healed or you die,” Guido says.

Another difference is that childhood cancer treatments can lead to debilitating side effects later in life. “Strong chemotherapy affects normal growth,” Guido says, adding that it can damage the lungs, brain and other organs, and can even cause secondary cancers.

While Guido has relatively few side effects since he was so ‘old’ when Ewing sarcoma hit, he is still at risk. He recently enrolled in a program for childhood cancer survivors at Children’s Medical Center of Dallas, where he lives now.

Called After the Cancer Experience, the program gives personalized follow-up care based on the chemotherapy used. This is because different drugs cause different problems. “They try to catch side effects as early as possible to prevent or delay damage,” Guido says. The program also collects data on outcomes. “This is important for future cancer patients because we don’t know much about this, and physicians make decisions based on statistics,” he explains.

Now a cancer researcher at the University of Texas Southwestern Medical Center, Guido hopes his work will someday help other people who face cancer. His personal experience with cancer also gives him a different viewpoint from his colleagues.

“They look at increased survival after treatment and say it’s a success — but patients also consider every single case for whom the therapy does not work, and criteria other than mere survival such as quality of life,” he says. “I think that I connect to this better than other researchers, and my experience is a constant reminder that there are significant unmet needs to work on.”