This study evaluates the addition of an alginate based solution to twice daily proton pump inhibitor therapy (PPI) in patients undergoing ablative therapy for dysplastic Barrett's esophagus. The investigators hypothesize that the addition of this medication will help to achieve complete remission of Barrett's over a shorter period of time.

Barrett's esophagus (BE) is a pre-cancerous condition in the esophagus that results from constant acid exposure and is a precursor to esophageal adenocarcinoma (EAC). Surprisingly, EAC rates continue to rise despite efforts aimed at addressing BE. Patients with dysplastic BE are at increased risk for developing EAC and in high grade dysplasia (HGD), this risk can be as high as 6% per year. For these reasons, these patients are candidates for ablation therapy, either with cryotherapy, endoscopic mucosal resection (EMR), and/or radiofrequency ablation (RFA). In patients receiving ablative therapy, 3-5 treatments are typically required before there is resolution of all Barrett's epithelium while patients remain on twice daily proton pump therapy.

A recent case study by the current authors demonstrated initial failed response of BE with HGD to RFA and subsequently cryotherapy. Only after initiation of a liquid alginate solution (Gaviscon Advance - UK formulation) was there a subsequent rapid and complete response to therapy. This case suggests that liquid alginate provided additional esophageal protection allowing mucosal healing and an overall enhanced response to treatment. This finding is mechanistically plausible given existing evidence demonstrating the carcinogenic properties of bile acids and injurious activity of pepsin in non-acid refluxate, and liquid alginate's unique ability to control these components and inhibit acid reflux. The investigators feel further investigation is warranted in studying the role of adjunct liquid alginate solution in patients undergoing treatment for BE.

The ingredient of interest in is alginic acid (alginate), a polysaccharide found in the cell walls of brown algae. Alginates are unique in their ability to form a protective layer above gastric contents upon exposure to gastric acid, thus limiting exposure of esophageal epithelium to gastric acid, bile acid, pepsin, and other parts of the gastric contents. Concurrently, the bicarbonate in alginate-based solutions forms carbon dioxide in the presence of gastric acid, which converts the gel into foam which floats to the surface of the gastric contents. Hence, alginate solutions form "rafts" which provide a physical barrier to acid reflux, as well as a pH-neutral substitute which refluxes preferentially over gastric acid.

Inclusion Criteria:

• (1) Age 18 (2) Biopsy-proven complicated BE (low/high grade grade dysplasia or IMC, confirmed by our institution's GI pathologist) As part of standard of care, all patients' biopsies will be confirmed with the institutions' GI pathologist and, either with outside biopsies or from biopsies completed at the primary institution.

Exclusion Criteria:

• 1) Moderate to severe renal impairment, as defined by eGFR< 60 for 2 consecutive readings (2) Lack of capacity for decision-making (3) Allergy to hydroxybenzoates (4) Patients with uncontrolled hypertension or decompensated heart failure (5) Pregnancy- patients of child-bearing potential will be tested. (6) Patients with elevated calcium or potassium on screening laboratory testing (labs completed within the last month)

Adverse Event Data was collected for eighteen months on each patient who was enrolled in the study. AE data was not collected for the historical control group since they were not actively enrolled onto the study, but their data from previous treatment was used to compare with the active participants.

Definition does not differ.