Molecular evaluation of ablative therapy of Barrett's oesophagus

Barrett's oesophagus is a major risk factor for developing oesophageal adenocarcinoma. Ablation by argon plasma coagulation (APC) and photodynamic therapy (PDT) is currently under investigation for the removal of metaplastic and dysplastic Barrett's oesophagus. This study examined the effect of ablative therapy on Barrett's oesophagus at cell-cycle and genetic levels. The premalignant potential of residual or recurring Barrett's oesophagus was assessed by p53 immunohistochemistry, Ki67-related proliferative capacity, and DNA ploidy status (ie an abnormal chromosome 1 number) as measured by interphase in situ hybridization. Twenty-nine patients with Barrett's oesophagus (23 male and 6 female, mean age 58 years, mean length of Barrett's oesophagus 4 cm) were treated with APC or PDT. Intestinal metaplasia without dysplasia was present in 16 patients, low-grade dysplasia in five, and high-grade dysplasia in eight patients. Biopsy samples were obtained at regular intervals (mean follow-up 20 months, range 6-36 months). One month after the first ablation, Barrett's oesophagus was no longer identified, either endoscopically or histologically, in nine patients (32%). At this time point, significant down-grading was achieved for abnormal chromosome 1 numbers (p = 0.020) and Ki67-defined proliferation (p = 0.002). Patients with residual Barrett's oesophagus were additionally treated with APC, resulting in the elimination of Barrett's oesophagus in 76% of all patients. However, at the last follow-up endoscopy, metaplasia without dysplasia was still present in five patients, and low- and high-grade dysplasia were each present in one patient. An abnormal chromosome 1 number and p53 protein overexpression were detected only in the high-grade dysplastic lesion, but increased proliferation was still present in the majority of these persisting cases. Although endoscopic removal of Barrett's oesophagus by ablative therapies is possible in the majority of patients, histologically complete elimination cannot be achieved in all cases. Persistent Barrett's oesophagus may still harbour molecular aberrations and must therefore be considered still to be at risk of progression to adenocarcinoma.