ESTRO 2025 Congress report I Radiobiology track

During ESTRO 2025, I had the privilege, with Dr Emilie Alvarez-Andres (OncoRay, Dresden, Germany), to chair the symposium named “Radiation Biology of Targeted Radionuclide Therapy”. During this session, the (immunological) effects of targeted radionuclide therapy (TRT) were compared with those of external beam radiation therapy (EBRT). While the application of TRT has increased over time with the availability of increasing numbers of targeting compounds (antibodies, peptides, small molecule inhibitors) and radionuclides, radiobiological knowledge that has been obtained from decades of research into EBRT is not necessarily transferable to TRT.

Dr Julie Nonnekens, from the Erasmus University Medical Center (Rotterdam, The Netherlands) and chair of the Dutch Society for Radiobiology, started with a presentation entitled “Radiobiological comparison of different radiation qualities: Alpha vs. beta vs. external beam radiation”. She indicated that in TRT, both alpha and beta emitters can be used, with greatly differing linear energy transfers (LETs) and types of damage. The radiobiological consequences and pros and cons of the use of each particle were discussed.

Dr Samantha Terry (King’s College London, London, UK) presented on “Radiation biology of Auger emitters”. Auger electrons are emitted by isotopes that decay via electron capture or internal conversion, producing cascades of very low-energy electrons that deposit their energy over distances of the order of nanometres. Therefore, these electrons have high LETs, but also need to be bound to cells to damage critical structures such as DNA and cell membranes. Like alpha emitters, Auger electrons induce particularly clustered DNA damage and show promising effects at the metastasis level.

Professor Dr Sandra Heskamp (Radboud University Medical Center, Nijmegen, The Netherlands) talked about the immune effects of radionuclide therapy. TRT-induced cell death can be immunogenic; this is also being extensively investigated in EBRT. This effect activates an anti-tumour immune response that could contribute to both local and distant control. However, the protracted, low-dose-rate irradiation that is inherent to TRT, modulated by the physical and biological half-life of each radionuclide, raises questions about the timing, magnitude, and durability of these immune effects, which remain under active investigation.

Paul Span

Radboud University Medical Center,

Nijmegen, The Netherlands

From left to right: Samantha Terry, Julie Nonnekens, Paul Span, Sandra Heskamp