highly significantP = 3.3 × 10 −4
2d ), showing a highly significant association between ecDNA in Barrett’s oesophagus biopsies and progression to EAC (Fisher’s exact test, P = 3.3 × 10 −4 , one-sided). ecDNA can arise in high-grade dysplasia The design of the longitudinal case–control FHCC study enabled the timing of ecDNA development in Barrett’s oesophagus segments to be determined in patients with a cancer outcome.