Pilot Human Study of a Balloon-based Bipolar Electrode for Ablation of Esophageal Epithelium: Results in Subjects Prior to Planned Esophagectomy

Abstract

Aims: To evaluate the histological effect of a balloon-based bipolar RF electrode ablation system on human esophageal squamous epithelium 24-48 hours prior to esophagectomy. Methods: This was an IRB-approved study. Enrolled subjects had been scheduled for esophagectomy and underwent ablation of 2 segments of epithelium 24-48 hrs prior to surgery. At EGD using conscious sedation, 2 separate 1-3 cm sites in the esophageal body were targeted. A series of sizing balloons determined the inner diameter of each site. A balloon-based bipolar electrode (BARRx, Inc., Sunnyvale, CA) was then positioned at each ablation site, and inflated. Energy was delivered using high power (260-350 W) and low energy density (10 or 12 J/cm2). At surgery, esophageal adventitia and mediastinum were inspected for thermal injury/inflammation. Longitudinal sections were obtained from each ablation zone (H and E). Completeness, uniformity and depth of ablation were assessed histologically. Results: Three male subjects were enrolled (age 55-70 yrs). All procedures were performed using conscious sedation (mean midazolam 7 mg, mean fentanyl 158 μg). Procedure time for each case was 60, 26, and 27 minutes respectively. There were no acute complications. One subject treated with 12 J/cm2 had esophageal discomfort 4 hours after treatment. At surgery, there was no evidence of pleural effusion, esophageal edema or adventitial injury. In one subject, some areas within the treatment zone were not ablated due to poor contact with the electrode, due to tumor related esophageal dilation, while others had uniform epithelial ablation. Ablation involved the lamina propria or muscularis mucosae in most sections, sparing the submucosa. While submucosa was not ablated, there was evidence of lymphocytic infiltration in some sections, especially at the 12 J/cm2 setting. Ablation was slightly deeper for 12 J/cm2 than for 10 J/cm2. Conclusion: This is a pilot evaluation of a novel balloon-based bipolar electrode for the ablation of esophageal epithelium. The procedure was well tolerated by subjects and utilizes existing endoscopic skills. 10 and 12 J/cm2 resulted in either complete ablation or significant full-thickness injury of the treated epithelium. Ablation depth was limited, at its deepest, to muscularis mucosae, although submucosal lymphocytes were present in some sections. This technique is currently being evaluated in a multi-center trial for the ablation of intestinal metaplasia.