Fast electrons for the future of radiation therapy

A research team from The Institute of Cancer Research, London and the Royal Marsden NHS Foundation Trust, together with DESY, has explored how ultra-intense electron beams could be harnessed for future cancer treatments. The study centers on PITZ (the Photo Injector Test Facility) at DESY’s Zeuthen site. The findings demonstrate that the facility’s highly intense, precisely controllable electron beam can be used in computer simulations to calculate dose distributions for superficial brain metastases—outperforming current methods. The results were published in the journal Physics in Medicine & Biology.

Radiation therapy remains one of the most critical tools in cancer treatment. The goal is always the same: to target tumor tissue as effectively as possible while minimizing damage to healthy tissue. One promising approach is FLASH radiotherapy, where the radiation dose is delivered not over minutes, days, or weeks, but in a fraction of a second. Preclinical studies suggest this method may reduce harm to healthy tissue while preserving its effectiveness against tumors. Similarly, recent years have shown that spatially fractionated radiation therapy (SFRT)—a technique that creates a grid of high-dose points—can also destroy tumours while sparing surrounding healthy tissue. The present study provides a basis for developing the combination of both methods for the benefit of cancer patients.

Originally built to advance modern accelerator technologies, PITZ at DESY in Zeuthen produces electron beams with dose rates far exceeding those of today’s clinical devices. This makes the facility a uniquely valuable testbed for deepening our understanding of the physical and biological principles behind FLASH irradiation.

“This study is a key step toward harnessing the unique capabilities of our accelerator technology to advance cancer radiotherapy at DESY,” says Frank Stephan of DESY, head of PITZ and co-author of the publication. “We demonstrate that PITZ’s electron beam can be effectively integrated into realistic treatment planning—a critical prerequisite for systematically developing the potential of FLASH and SFRT therapies and their combination.”

For the study, the team in London developed a mathematical model of the electron beam and combined it with a fast computational method for dose calculation. At PITZ, the 17.5 MeV electron beam was first measured in a water phantom—a specialized container filled with water that acts as a stand-in for human tissue and is a standard procedure for assessing radiation distribution in the body. The calculated dose distributions matched the measurements within the experimental uncertainty of three percent.

The researchers then applied the method to anonymized patient data from six individuals with superficial brain metastases. Such metastases, located near the skull’s surface, are a particularly suitable case for electron beams, whose penetration depth is limited. The calculated treatment plans using scanned electron beams were compared with established methods, including photon irradiation with a robotic CyberKnife system and various proton therapies.

The simulations showed that the scanned electron beams could be precisely targeted to the treatment volume. In the cases studied, they achieved better dose conformity to the target area for superficial brain metastases than the other methods. At the same time, the calculated doses for healthy brain tissue and skin remained within acceptable limits.

At this stage, the work remains a planning and feasibility study, not yet a clinical treatment. However, the results suggest that combining a rapid sequence of electron pulses, beam deflection, and advanced dose calculation could be a promising path toward preparing future cancer therapies using FLASH and SFRT.

“The key point is that we now have a better understanding of which treatment geometries are fundamentally possible with such a beam,” explains Matthias Gross of DESY, coordinator of radiation studies at PITZ and co-author of the study. “This lays the groundwork for the next steps—from further physical measurements to biological investigations and, ultimately, the question of which clinical applications might be realistic in the long term.”

The work aligns with DESY’s growing activities at the intersection of accelerator physics, medical physics, and biomedical research. Modern particle accelerators are not only tools for fundamental research but can also open new technological avenues for diagnostics and therapy.

DESY Accelerator Director Wim Leemans says: “FLASH and SFRT research exemplify this particularly well: they combine cutting-edge accelerator technology with one of modern medicine’s central challenges—treating cancer more effectively while minimizing harm to healthy tissue.”

DESY Astroparticle Physics Director Christian Stegmann, who leads the Zeuthen campus, says: “Radiation therapy could be taking a new and unprecedented step forward with this technology, developed here in Zeuthen. This result is a sign that we are moving in an excellent direction as we bring this potential treatment closer to application.”