FLASH Radiotherapy — Breaking the Speed Barrier of Radiobiology
By 2026, FLASH Radiotherapy (FLASH-RT) has transitioned from a lab curiosity to human clinical trials (such as the FAST-02 and NCT05724875 studies). FLASH delivers radiation at ultra-high dose rates—typically $\ge 40$ Gy/s—completing an entire treatment in less than 200 milliseconds.
The "FLASH Effect" and Healthy Tissue Sparing: The primary clinical breakthrough of 2026 is the confirmation of the "FLASH Effect." At these extreme speeds, normal tissues exhibit significantly higher resistance to radiation damage compared to conventional rates.
The Oxygen Depletion Hypothesis: One leading theory being validated in 2026 is that FLASH radiation consumes tissue oxygen so rapidly that it creates a transient state of microscopic hypoxia. Since oxygen is a potent radiosensitizer, this temporary "suffocation" protects healthy cells, while the tumor—which is already hypoxic and adapted to low oxygen—remains vulnerable to the lethal dose.
Logistical Revolution: Because a treatment course that once took 30 days can now be delivered in a single sub-second burst, FLASH-RT has the potential to triple the patient capacity of oncology centers, effectively solving the global bottleneck for radiation access.