FLASH Radiotherapy

What is FLASH Radiotherapy?

FLASH radiotherapy is a revolutionary approach to cancer treatment that delivers ultra-high dose radiation in less than a second—over 100 times faster than conventional methods. Originally observed decades ago but rediscovered in the 2010s, this delivery method shows a remarkable ability to kill cancer cells while protecting healthy tissue. It's currently under clinical investigation, with early results that could transform how we treat brain tumors like DIPG and DMG.

Why FLASH is a Game-Changer for Children

Children’s developing brains are highly sensitive to radiation. Traditional radiation therapies can damage healthy tissue, leading to long-term neurocognitive and developmental side effects. FLASH radiotherapy may offer a better way.

“FLASH isn’t just an improvement in technology, it’s a shift in biological thinking. It widens the therapeutic window, allowing us to treat tumors that were previously untouchable because of the risks to surrounding healthy tissue.” 
– Dr. Anthony Mascia, Chief Physicist and Director of the Proton Therapy Center at Cincinnati Children’s Hospital
  • Spares healthy tissue: FLASH appears to reduce radiation-induced damage to organs and brain structures, like the hippocampus, critical for memory and executive function.
  • Delivers equivalent or better tumor control: Animal studies show that FLASH is at least as effective as conventional methods at killing tumors, even aggressive ones.
  • May supercharge the immune system: Early data suggest FLASH may enhance immune response against tumors, potentially aiding in long-term control.
  • Shortens treatment time: Most FLASH treatments are delivered in fractions of a second, reducing sedation needs for pediatric patients.

Real-World Results: What We Know So Far

In preclinical and early-phase clinical studies operated by Cincinnati Children's Hospital's proton team:

  • Mice receiving FLASH showed 100% survival at doses where 50% of those receiving conventional radiation died.
  • Blood tests and skin reaction assessments showed markedly less toxicity under FLASH.
  • In juvenile brain models, FLASH preserved learning and memory function, a critical advantage for pediatric use.
  • Studies showed FLASH may work with fewer beams or higher single doses, possibly opening the door to shorter treatment regimens.

FLASH also continues to show no reduction in tumor-killing ability. That means clinicians could increase the dose to the tumor—a strategy known as dose escalation—without raising risk to healthy tissue. For a tumor like DIPG or DMG, where location limits safe dosing, this is potentially groundbreaking.

Understanding the Bragg Peak

Unlike standard X-rays, which pass straight through the body, protons can be precisely stopped at a specific depth. The point where most of the radiation is delivered is called the Bragg peak. By adjusting the proton beam’s energy, doctors can target tumors with high doses while minimizing exposure to healthy tissue behind the tumor.

What Comes Next?

Researchers are now asking:

  • Can FLASH be delivered using Bragg peak technology, to further localize dose?
  • Can it be safely combined with chemotherapy or immunotherapy?
  • Will fractionation (multiple smaller doses) preserve the FLASH effect?
  • What is the best clinical trial design for DIPG/DMG?

As Dr. Mascia explained, their goal is clear:

“We don’t just want to spare normal tissue, we want to change what’s possible in treating these cancers.”

FLASH and DIPG/DMG: A Vision for the Future

DIPG and DMG are notoriously difficult to treat due to its location and resistance to conventional therapies. FLASH radiotherapy offers a new pathway—one that may allow oncologists to deliver higher doses directly to the tumor without overwhelming surrounding structures like the brainstem.

While FLASH is still experimental and not yet available for DIPG/DMG treatment, clinical trials are underway to test its safety and potential in pediatric brain tumors. The hope is that one day, FLASH will provide a safer, more effective option for children facing this devastating diagnosis.

Summary

FLASH radiotherapy isn’t just faster—it may be smarter. By protecting healthy tissue while maintaining potent tumor control, it opens a new chapter in pediatric brain cancer care. Thanks to pioneering research and international collaboration, a future where DIPG patients receive safer, more effective radiation treatment is on the horizon.