Stanford Medicine Launches First-of-Its-Kind Compact Proton Therapy System, Treats First Pediatric Patient
Key Insights
Stanford Medicine Cancer Center (search) has launched a compact proton therapy system developed by Mevion Medical Systems (search), the first of its kind to fit in a single treatment room.
The system's miniaturized design using superconducting magnets reduces costs to approximately $33 million, roughly one-tenth that of larger proton systems.
A 7-year-old boy with a rare brain stem tumor (search) became the first patient treated with the new device, highlighting proton therapy's importance for pediatric cancers.
Stanford Medicine Cancer Center (search) has launched a compact proton therapy system that represents a significant technological leap in radiation oncology, with a 7-year-old boy becoming the first patient treated in the Bay Area since the 1990s.
Stephen De La Torre, diagnosed with a rare tumor attached to his brain stem, completed his course of proton therapy this month at Stanford Medicine's cancer center in Palo Alto. The boy's case underscores why the treatment matters: proton therapy delivers cancer-killing radiation with precision that spares healthy surrounding tissue — a critical advantage for pediatric patients whose developing bodies are especially vulnerable to radiation's long-term effects.
"It's really this whole white part that's the tumor," said Dr. Susan Hiniker, director of pediatric oncology at Stanford Medicine. "It's a whole other set of things that we need to think about when treating a child, including effects on growth. And as part of the long-term toxicity profile. You know, these are kids. We want them to live 90 more years, and they may be dealing with the effects of treatment for the rest of their lives."
A Miniaturized Breakthrough
The new system, developed by Massachusetts-based Mevion Medical Systems (search), represents a dramatic departure from traditional proton therapy infrastructure. Historically, proton therapy machines have been enormous — earlier generations relied on cyclotrons encased in concrete several stories high. The New York Proton Center, which opened in 2019, installed its system for more than $300 million, with a cyclotron weighing 90 tons and rotating gantries each weighing 280 tons.
"The advantage of proton therapy is that it allows us to concentrate radiation dose in tumors, and less in the surrounding normal organs," said Dr. Billy Loo, a Stanford Medicine radiation oncologist. "Proton therapy historically has always involved very large machines, meaning that you have to essentially build a new building around it."
The Mevion system changes that calculus. Using superconducting magnets, the technology has been miniaturized to fit in treatment rooms that previously housed conventional X-ray radiation devices. The particle accelerator is just six feet wide. Mevion CEO Tina Yu said the system cost Stanford $33 million — roughly one-tenth the cost of some larger proton systems.
First Patient: A Pediatric Case
De La Torre's treatment journey illustrates the clinical rationale for proton therapy. The boy had already completed a four-week course of conventional X-ray therapy before the proton device became operational. His care team then incorporated proton therapy into his treatment plan.
"Every little edge we can get, we can take advantage of," Loo said.
Most cancer patients receive X-ray radiation, which enters the body and exits the other side, exposing healthy tissue and organs along its path. Protons, by contrast, stop at the tumor, depositing their energy precisely where needed. This distinction is particularly meaningful for children, who may live decades after treatment and could require radiation again in the future.
"In many patients, especially those who are growing and developing or have tumors in certain areas, or have had previous radiation, that can be really important," Hiniker said.
De La Torre's mother, Tricia LaBrasca, reported that her son experienced remarkably few side effects. "It hasn't slowed him down much," she said. "He gets a little groggy after treatments, but he hits the ground running every day."
Regulatory and Clinical Milestones
The U.S. Food and Drug Administration approved the Mevion device for clinical use in 2025. Its deployment at Stanford marks its first real-world application with patients.
"You can do a lot of things on paper," Mevion CEO Tina Yu said. "But can you do it with a seven-year-old boy?"
Charles Simone, chief medical officer at the New York Proton Center, described the compact system as a "first of its kind" breakthrough, noting that hospitals should be able to incorporate proton therapy more easily by converting existing radiation vaults, as Stanford did.
Expanding Access
Stanford's team believes the clinic will make proton therapy more accessible for patients who previously had to travel long distances. Until now, patients in the Bay Area whose doctors recommended proton therapy had to travel hundreds of miles for treatment. About 50 U.S. centers and hospitals currently offer proton therapy.
The Stanford team is working with the manufacturer on final preparations and expects to begin treating additional patients as early as this summer. De La Torre will return to Stanford in late July for an MRI to assess how his tumor responded to the treatments.