Background: Extrachromosomal DNA (ecDNA) amplification represents a distinct mechanism of genomic instability in cancer, increasingly recognized for its role in aggressive disease progression. This review examines how ecDNA drives tumour evolution and assesses its potential as both a prognostic marker and therapeutic target. Methods: The authors integrate findings from multiple detection platforms—including FISH, whole-genome sequencing, and specialized reconstruction algorithms—and present data across diverse cancer types; no preregistration is noted, and no animal studies are included. Results: ecDNA consists of circular, acentric DNA elements carrying high-copy oncogene amplifications (such as EGFR, MYC, MDM2, and CDK4). Unlike chromosomal DNA, ecDNA segregates unevenly during cell division, generating intratumoral heterogeneity, accelerating adaptation to selective pressures, and promoting resistance to therapy. Pan-cancer surveys summarized here reveal ecDNA in a significant subset of tumours, with particularly high frequencies in liposarcoma, glioblastoma, and HER2-positive breast cancer, and consistent associations with worse clinical outcomes. Conclusions: The authors conclude that ecDNA amplification serves as a credible adverse prognostic indicator and holds promise for refining risk stratification and guiding treatment strategies. However, they stress that clinical adoption remains constrained by the absence of standardized, scalable, and reproducible detection.
Gajewski et al. (2026) studied this question.