Chromoendoscopy with methylene blue and associated DNA damage in Barrett's oesophagus.

Chromoendoscopy with methylene blue has been proposed to improve targeting of biopsies to specialised intestinal metaplasia and dysplasia in Barrett's oesophagus. However, methylene blue can induce oxidative damage of DNA when photosensitised by white light. We show that damage to DNA is increased in Barrett's mucosa after chromoendoscopy with methylene blue, an effect apparently dependent on presence of both methylene blue and endoscopic white light. Exposure of Barrett's mucosa to DNA damage during endoscopy warrants caution since it could accelerate carcinogenesis. This risk needs to be carefully balanced against the possible benefit of improved early detection of preneoplastic lesions with methylene blue chromoendoscopy.