In patients with Barrett’s esophagus, use of proton pump inhibitors (PPIs) did not lead to dysplasia- or cancer-protective effects.
http://www.empr.com/news/proton-pump-inhibitors-dysplasia-adenocarcinoma-barretts-esophagus/article/631058/
Do PPIs Protect Against Dysplasia, Cancer in Barrett’s Esophagus?