Liquid biopsy of plasma and urinary CfDNA differentiates glioma recurrence from radiation brain necrosis in preclinical models

It is difficult to differentiate between glioma recurrence and radiation brain necrosis after radiotherapy in the clinic, but it is very important for patients. The purpose of this study is to observe the clinical significance of cell-free DNA (cfDNA) in the differential diagnosis between them based on liquid biopsy. The SD rats were used to establish a glioma recurrence model and a radiation brain necrosis model. The successful establishment of the two models was verified by MRI, IVFI, HE staining, immunofluorescence and immunohistochemistry. Then, the changes of cfDNA in the two models (B1-SINE in plasma and mtDNA in urine) were analyzed by qPCR. After ionizing particle irradiation, qPCR results showed that the level of mtDNA in urine increased significantly at the 6th week and reached the peak at the 8th week. The B1-SINE of plasma samples increased significantly at the 4th week of irradiation and reached the peak at the 8th week. From week 8 to week 16, when radiation necrosis occurred, the levels of mtDNA in urine and B1-SINE in plasma increased significantly (p < 0.01). In the glioma recurrence model, there was no significant difference in urinary mtDNA level and plasma B1-SINE level between the normal group and the sham surgery group (p > 0.05). These findings demonstrate that cfDNA liquid biopsy, represented by plasma B1-SINE and urinary mtDNA, holds significant clinical translational potential as an early differential diagnostic marker for radiation-induced brain necrosis and glioma recurrence, warranting further validation of its sensitivity and specificity through ROC analysis in clinical samples.