Efficacy and toxicity of FLASH radiotherapy: A systematic review

In recent times, research on the use of ultrahigh-dose rates delivered in super-fast times in cancer treatment has been garnering interest. This has brought about the term "FLASH" radiotherapy (RT). Thus, in the present study, we systematically review these recent studies on FLASH RT with regard to its efficacy and safety. The reporting of this systematic review was done in line with the statement of Preferred Reporting Items for Systematic reviews and Meta-Analyses. Electronic search of the databases such as PubMed, Scopus, and Embase was conducted to retrieve relevant studies investigating the FLASH effect. From an initial search of 216 potential articles, 16 articles (in vivo, in vitro , and clinical studies) were finally included in this systematic review. Results showed that FLASH RT dose rates had protective effects on normal tissues in addition to antitumor effect. Although still in its early research stages, FLASH RT has the potential to rival present RT regimens in terms of safety and antitumor effect. However, further studies are needed to address the aspects such as optimal dose rate, effect on deep tumors, tumor recurrence, longer follow-up time, and mechanism of action.