Young California cancer victim’s battle could eventually save lives

Sebastian Guerra was an otherwise typical 10-year-old who faced an extraordinary battle with bravery. He was diagnosed with diffuse midline glioma, an inoperable brain tumor, and was given a grim prognosis.

“They looked at me and they said, ‘I’m so sorry your son has this type of tumor… and it’s very aggressive,’” Kathryn Mosier, Sebastian’s mother, told KTLA. Doctors said Sebastian would be lucky to make it to his 11th birthday. His only hope came from a clinical cancer trial, which he was approved to join, and the early results were encouraging.

Mosier said her son was nearly symptom-free for more than 10 months.

Dr. Ashley Plant-Fox, who spent eight years developing the trial, explained how the treatment works. “It’s basically targeting 16 unique neoantigens or markers on the tumor cells to try and to get the immune system to recognize that it’s foreign and attack it,” she said.

The trial is being conducted at four sites in North America, including Children’s Hospital of Orange County (CHOC).

“We hope that this will be the answer, and this will be the cure for kids,” said Claudia Mousa, director of clinical research coordinators for oncology research at CHOC.

Despite the promising start, Sebastian’s condition worsened, and he passed away shortly after his 11th birthday. His tumors were donated to Stanford University for future research.

The trial and others like it face challenges due to recent cuts in federal funding for pediatric cancer research, shifting the burden to private donations, which researchers say is not sustainable.

“There are actually patients on those trials that will have to stop treatment at the end of 2025,” Plant-Fox noted.

Sebastian’s legacy continues through the donation of his tumors and monetary donations to support pediatric cancer research. To donate:

• Pediatric Cancer Research Foundation
• Team Jack Foundation
• Lurie Foundation: KBraden@luriechildrens.org