Circulating Alu Elements as Biomarkers for Radiation-Induced Toxicity in Cancer

), aligning with increased loss of heterozygosity and exon mutational burden. In addition, Alu hypomethylation further promotes microsatellite instability, recombination, defective repair, and is associated with therapeutic resistance. In parallel, circulating cell-free DNA fragments containing Alu sequences have also been correlated with delivered radiation dose and clinical toxicity, underscoring their potential as minimally invasive biomarkers. Taken together, these findings position Alu activation as both a mechanistic driver of radio-response heterogeneity and a minimally invasive biomarker for biodosimetry and toxicity risk stratification.