There are two hypotheses: (1) Consecutive thermal ablation of metaplastic, non-neoplastic long segments of Barrett's esophagus (>2cm)plus esomeprazole after successful endoscopic therapy of mucosal cancer by means of ER will decrease the incidence of secondary cancer (local recurrence and metachronous cancer) by a minimum of 50% compared to acid suppression alone without ablation within a 5-years follow-up (primary endpoint). (2) After successful ablation of Barrett's esophagus patients need ongoing acid suppression therapy for medical control of their underlying reflux disease (secondary aim of the study).