Background: Radiofrequency ablation (RFA) has been used effectively for the treatment of Barrett’s esophagus. This technology may additionally have a role in the treatment of bleeding or neoplasia in the lower GI tract. The goal of this study was to determine the optimal treatment parameters to create ablative effect to the colonic mucosa/submucosa, without deeper transmural colonic injury.
Methods: In this IRB approved protocol, patients undergoing elective left colon or rectal resection were enrolled. Once margins of resection were determined intra-operatively, a colonoscope mounted with a planar RFA device (HALO90, BÂRRX Medical) with a 13mm by 20mm bipolar array was advanced to the resection segment. Areas of normal mucosa were ablated in situ with 2 or 4 applications (APP) while varying energy density (12, 15, or 20 J/cm2). After removal with the surgical specimen, ablation zones and untreated normal adjacent tissue were multiply sectioned and stained with H&E. An expert GI pathologist, blinded to the treatment parameters, assessed the deepest histological layer with any histopathological change (inflammation, ablation, abnormal pattern, necrosis.)
Results: We created 51 ablations zones in 16 patients. When comparing max depth of histological change in 2 vs. 4 APP, regardless of energy density, evidence of serosal change occurred in 0% (0/24) vs. 15% (4/27) of zones (p=0.11), whereas changes to the muscularis propria (MP) occurred in 25% (6/24) vs. 63% (17/27) of zones (p<0.05).Comparing energy density settings of 12, 15, and 20 J/cm2, regardless of APP, we observed an unexpected inverse relationship of energy vs depth, in that changes were present in MP in 74% (17/23), 35% (6/17), and 0% (0/11), respectively (P<0.05); and in serosa in 9% (2/23), 12% (2/17), and 0% (0/11) (P=0.517). No changes in serosa were seen in any 2 APP ablation zone at any energy density.
Conclusions: We observed a direct correlation between APP and ablation effect depth for this device in the colon. All ablation zones at 2 APP demonstrated no changes to the serosa and only a 25% incidence of MP changes. We observed an unexpected inverse relationship between energy and ablation depth, counter to reports in similar trials involving the esophagus. This observed variability may be due to inconsistent electrode approximation to mucosa, variable colonic wall thickness, and possible coagulum formation on the electrode preventing conduction of energy. This evaluation has identified a safe treatment parameter (12 J/cm2, 2 APP) that penetrates no deeper than MP, and will guide follow-up trials for disorders of the lower GI tract, including hemorrhagic radiation proctitis.