Advancements in Ultra-High Dose-Rate Radiation to Protect Normal Cells in Cancer Treatment

Researchers at the University of Osaka have achieved a significant breakthrough in the field of cancer radiotherapy by uncovering specific conditions where carbon ion beams, delivered at ultra-high dose rates (uHDR), can safeguard healthy cells during treatment. This phenomenon, termed the "FLASH effect," holds promise for transforming cancer therapy by minimizing side effects and enhancing patient quality of life.

Typically, radiation therapy is an effective method for targeting tumors, but it can inadvertently harm surrounding healthy tissues. The FLASH effect, first identified in 2014, demonstrates that delivering radiation at dose rates exceeding 40 Gy per second can effectively control tumors while sparing normal tissues.

While such effects have been observed with X-rays, electrons, and protons, evidence for similar protective effects using carbon ion beams—a modality known for its precision and high biological effectiveness—was limited. The challenge lay in creating controlled environments with ultra-high dose rates for carbon ions to explore this effect.

Using a specially adapted synchrotron system at the Osaka Heavy Ion Therapy Center, scientists irradiated different human cell types, including normal and cancerous cells, under various oxygen and linear energy transfer (LET) conditions. Remarkably, they found that even under normal oxygen levels, irradiation with uHDR carbon ion beams significantly increased the survival rate of normal cells compared to conventional dose rates. This protective "cell-sparing" effect was more pronounced at higher LET values (around 50 keV/μm), which are typical near tumor sites.

Further analysis revealed reduced DNA damage markers in cells exposed to uHDR irradiation, hinting at a distinct biological mechanism behind the protective effect. Lead researcher Kazumasa Minami emphasized, "This is the first time we have observed the cell-sparing effect with carbon ions under normoxic conditions," highlighting the potential for clinical applications.

The findings suggest that by fine-tuning parameters like dose, LET, and oxygen levels, it may be possible to deliver potent cancer treatments that cause fewer side effects. Future research aims to explore immune responses and tumor-specific effects, paving the way for more precise and safer radiotherapy options.

This breakthrough opens new avenues for integrating the FLASH effect into clinical settings, potentially revolutionizing how we approach cancer treatment with carbon ion therapy. Source: https://medicalxpress.com/news/2025-05-ultrahigh-dose-irradiation-cells-cancer.html