Cancer treatments for targeting tumor amplifications lag behind those targeting point mutations – and part of the reason may be that amplifications often reside on extrachromosomal DNA (ecDNA). Since ecDNA was first described back in 1965 as minute chromatin bodies in brain cancer cells, the use of large-scale DNA sequencing techniques has revealed the presence of ecDNA across a wide range of cancer types. “The circular structure of ecDNA is associated with increased proto-oncogenic capacity in comparison to linear amplifications. Another key feature is that ecDNA does not contain centromeres,” Roel Verhaak, from Yale School of Medicine, told the audience in a session at the 2023 AACR-NCI-EORTC Conference on Molecular Targets and Cancer Therapeutics in Boston.