Dresden, May 8, 2025 – Proton therapy, a highly precise method for treating brain tumors, carries risks due to the variable biological effectiveness of proton beams, despite its tissue-sparing properties. Researchers at the National Center for Radiation Research in Oncology – OncoRay in Dresden have now developed an approach to better estimate these risks and significantly reduce them through optimized planning procedures.
The biological effectiveness of protons, which indicates how much they damage tissue compared to photon beams, is clinically set at a flat rate of 1.1. However, studies show that it can be significantly higher locally, especially at the end of the beam path, endangering sensitive structures such as optic nerves or healthy brain tissue. "A fixed assumption of effectiveness can underestimate the burden on healthy tissue," explains Martina Palkowitsch, lead author of the study.
The OncoRay team, led by Prof. Steffen Löck, analyzed the treatment data of 105 patients treated with protons in Dresden between 2015 and 2022. Computer-aided simulations showed that in about one-third of cases, the risk of side effects such as visual disturbances or memory impairments was underestimated, especially for tumors near sensitive organs. Factors such as tumor size, age, or chemotherapy also influenced the risk.
The team tested two novel planning approaches that account for variable biological effectiveness and keep particularly effective radiation components away from sensitive structures. In six patients, including five with increased risk, the risk of side effects in endangered organs could be reduced by approximately 30 percent without compromising the effectiveness of tumor treatment.
The results, published by OncoRay, a collaboration between the Helmholtz-Zentrum Dresden-Rossendorf, TU Dresden, and University Hospital Dresden, mark an important step towards safer and more personalized proton therapies.
