Early radiobiological effects of flattening filter (FF) and flattening filter-free (FFF) beams and the radioprotective role of melatonin in rat brain: a preclinical study.

The study aimed to investigate early radiobiological effects of Flattening Filter (FF) and Fattening Filter-Free (FFF) beams on brain tissue in experimental rat models and to evaluate the potential radioprotective role of melatonin (MEL) using histopathological and biochemical parameters. Forty female Wistar albino rats were randomly assigned to five groups: control (G1), FF (G2), FF + MEL (G3), FFF (G4) and FFF + MEL (G5). A single 16 Gy dose was delivered to the head and neck region in G2 and G4. MEL (50 mg/kg) was administered intraperitoneally 15 minutes before irradiation in G3 and G5. Forty-eight hours post-irradiation, serum samples were analyzed for M30, M65, TAS, TOS and OSI. Brain and cerebellar tissues were histologically examined for neuronal degeneration, vascular dilatation, congestion, axonopathy, inflammation, dysplasia and necrosis. While M30, M65, TOS and OSI levels increased in G2 and G4 radiotherapy groups, TAS levels decreased for biochemical analyses (P < 0.05), reflecting impaired antioxidant capacity. However, these alterations were significantly reduced in the MEL-treated groups (G3 and G5) (P < 0.05). Histopathologically, neuronal degeneration, vascular dilatation and congestion were observed in G2 and G4 groups. MEL administration significantly alleviated these findings. No statistically significant differences were found between the FF and FFF groups regarding biochemical or histopathological outcomes (P > 0.05). While FF and FFF beams caused similar levels of oxidative stress and histopathological damage in the brain tissue, MEL treatment significantly reduced these damages. MEL emerges as a promising radioprotective agent against early radiation-induced brain injury.