FLASH Radiotherapy and Ultra-High Dose Rate Applications
Summary
FLASH radiotherapy is an emerging modality in which ionising radiation is delivered at ultra-high dose rates (typically >40 Gy/s) over very short time scales. Preclinical studies and early clinical forays have revealed a unique phenomenon, the FLASH effect, whereby normal tissues exhibit reduced toxicity compared with conventional dose‐rate treatment while tumour control is preserved. This differential response is thought to arise from rapid oxygen depletion, altered free‐radical chemistry and modulation of immune and inflammatory pathways. Technological advances in very high‐energy electrons, photon and proton delivery systems, alongside improvements in treatment planning and dosimetry, have enabled a range of experimental platforms for FLASH delivery. The global significance of FLASH lies in its potential to expand therapeutic windows, reduce side effects in paediatric and re-irradiation settings, and enable dose escalation for radioresistant malignancies. Ongoing efforts focus on elucidating radiobiological mechanisms, refining beam control, and translating these ultra‐fast modalities into clinical workflows.
Research from Nature Portfolio
Recent studies have highlighted the critical role of tissue oxygenation in mediating the FLASH effect. One investigation demonstrated that supplemental oxygen during anaesthesia abrogates the normal tissue sparing and impairs anti-tumour immune infiltration in both FLASH and conventional proton therapy, underscoring the importance of optimising oxygen levels for clinical protocols. Preclinical work in abdominal irradiation models has shown that single‐fraction, total abdominal FLASH markedly reduces gastrointestinal syndrome, preserves epithelial integrity and stem cell viability, yet retains comparable tumour control in ovarian cancer metastasis settings. Complementary research into dosimetry for very high‐energy electron beams has revealed substantial ion recombination effects in plane-parallel ionisation chambers at high dose‐per‐pulse, prompting the development of revised calibration protocols to ensure accurate dose delivery in FLASH and related ultra‐high dose‐rate therapies.
FLASH Radiotherapy and Ultra-High Dose Rate Applications publication trend
The graph below shows the total number of articles in flash radiotherapy and ultra-high dose rate applications across all publications each year (not limited to Nature Index journals).
Technical terms
FLASH radiotherapy: A radiotherapy technique delivering therapeutic doses at ultra-high dose rates (typically >40 Gy/s) in sub-second exposures to exploit differential normal-tissue sparing.
Ultra-high dose rate (UHDR): The rate of radiation delivery greatly exceeding conventional clinical settings, usually above 40 Gy/s, enabling unique radiobiological effects.
Oxygen depletion hypothesis: A model proposing that rapid consumption of molecular oxygen during FLASH irradiation reduces free-radical fixation of DNA damage in normal tissues.
Bragg peak: The sharp maximum in energy deposition by charged particles, such as protons, at the end of their range, critical for conformal dose delivery.
Pencil beam scanning: A proton therapy delivery method using narrow, magnetically steered beams to paint dose distributions, adaptable for ultra-high dose-rate applications.
References
- Oxygen supplementation in anesthesia can block FLASH effect and anti-tumor immunity in conventional proton therapy. Communications Medicine (2023).
- Abdominal FLASH irradiation reduces radiation-induced gastrointestinal toxicity for the treatment of ovarian cancer in mice. Scientific Reports (2020).
- The challenge of ionisation chamber dosimetry in ultra-short pulsed high dose-rate Very High Energy Electron beams. Scientific Reports (2020).
- Current views on mechanisms of the FLASH effect in cancer radiotherapy. National Science Review (2024).
- Ultra-High Dose Rate (FLASH) Radiotherapy: Silver Bullet or Fool's Gold?. Frontiers in Oncology (2020).
- FLASH Proton Radiotherapy Spares Normal Epithelial and Mesenchymal Tissues While Preserving Sarcoma Response. Cancer Research (2021).
About these summaries
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