Effects of Lugol staining on stenosis formation induced by radiofrequency ablation of esophageal squamous epithelium: a study in a porcine model

Extension of early esophageal squamous cell neoplasia into ducts and submucosal glands and the role of endoscopic ablation therapy

BACKGROUND AND AIMS

Early esophageal squamous cell neoplasia (ESCN) is preferably treated with en-bloc endoscopic resection. Ablation might be an alternative for flat ESCN, but ESCN extension along the epithelial lining of ducts and submucosal glands (SMGs) might jeopardize ablation efficacy. Clinical studies suggest that local recurrence might arise from such buried ESCN niches after ablation. We studied human endoscopic resection specimens of ESCN to quantify ESCN extension into ducts/SMGs and performed a prospective porcine study to evaluate the depth of radiofrequency ablation (RFA) and CryoBalloon ablation (CBA) into ducts/SMGs.

METHODS

Endoscopic submucosal dissection specimens of flat-type ESCN from a Japanese (n = 65) and Dutch cohort (n = 14) were evaluated for presence and neoplastic involvement of ducts/SMGs. Twenty-seven pigs were treated with circumferential RFA (c-RFA; n = 4), focal CBA (n = 20), and focal RFA (n = 3) with 4, 60, and 9 treatment areas, respectively. After prespecified survival periods (0 hours, 8 hours, 2 days, 5 days, and 28 days), treatment areas were evaluated for uniformity and depth of ablation and affected SMGs.

RESULTS

Neoplastic extension in ducts/SMGs was observed in most lesions: 58% (38/65) in the Japanese and 64% (9/14) in the Dutch cohort. In the animal study, 33% of SMGs (95% confidence interval, 28-50) were not affected after c-RFA, although the overlying epithelium was ablated. Focal RFA and CBA resulted in uniform ablations with effective treatment of all SMGs.

CONCLUSIONS

ESCN extends into ducts/SMGs in most patients. In an animal model, focal RFA and CBA effectively ablated SMGs, whereas c-RFA inadequately ablated SMGs. Given this potential reason for recurrence, endoscopic resection should remain the standard of care.

Endoscopic resection combined with the Cryoballoon focal ablation system in the porcine normal esophagus: a preclinical study

BACKGROUND

The Cryoballoon focal ablation system (CbFAS) for dysplastic Barrett's esophagus is simple, time-saving and has high therapeutic efficacy. This study aimed to evaluate the technical feasibility and tissue damage with combination therapy of endoscopic resection (ER) and CbFAS in porcine models.

METHODS

Three pigs (A, B, and C) were included, and all ER procedures were performed by endoscopic mucosal resection using the Cap method (EMR). Combination therapy for each pig was performed as follows: (a) CbFAS was performed for a post-EMR mucosal defect for Pig A; (b) CbFAS for post-EMR scar for Pig B, and (c) EMR for post-CbFAS scar for Pig C. All pigs were euthanized at 32 days after the initial procedure, and the tissue damage was evaluated.

RESULTS

All endoscopic procedures were followed as scheduled. None of the subjects experienced anorexia, rapid weight loss, bleeding, and perforation during the observation period. They were euthanized at 32 days after the initial endoscopic procedure. On histological assessment, there was little difference between the tissue that was treated with CbFAS alone and that treated with CbFAS in combination with ER.

CONCLUSION

Combination therapy with ER and CbFAS can be technically feasible, and its outcome was not significantly different from CbFAS alone in terms of tissue damage.

Single-Step Treatment with Limited Endoscopic Resection and Cryoballoon Ablation Is Feasible and Safe in an Esophageal Porcine Model

BACKGROUND

Treatment of Barrett's neoplasia consists of two steps: endoscopic resection of visible lesions with subsequent ablation of remaining Barrett's epithelium. However, extensive resection might hamper subsequent ablation due to stenosis. Combining both modalities in one session therefore offers potential advantages. Single-step treatment with radiofrequency ablation and resection appeared to be unsafe.

AIMS

To evaluate feasibility and safety of single-step treatment with cryoballoon ablation and endoscopic resection.

METHODS

Two single-step treatment regimens (15 treatment areas per regimen) were evaluated: (1) CRYO-EMR: four side-by-side focal ablations of 10 seconds followed by resection in the treated area; (2) EMR-CRYO: resection followed by 10-s ablation targeted on the resection wound. Primary outcome for both regimens was safety (perforations, clinically relevant strictures) and for CRYO-EMR also feasibility of resection and histopathological evaluation. Secondly, all CRYO-EMR and esophageal resection specimens were histopathologically evaluated.

RESULTS

Six female pigs were treated (five treatment areas per animal). During 28 days of follow-up, no perforations or clinically relevant stenosis occurred. All resections were technically successful. For all CRYO-EMR specimens, histopathological evaluation was feasible with ablation effects present throughout all layers, while the architecture requisite for histopathological analysis remained intact. After 28 days, histopathological evaluation of the esophagi was performed. For EMR-CRYO, post-treatment fibrosis was present throughout the submucosa. The muscularis propria was the deepest layer involved for CRYO-EMR.

CONCLUSIONS

Single-step treatment with limited endoscopic resection and cryoballoon ablation is feasible and safe in a porcine model and justifies further evaluation in a clinical trial.

Radiofrequency Ablation for Early Superficial Flat Esophageal Squamous Cell Neoplasia: A Comprehensive Review

Esophageal squamous cell carcinoma comprises the majority of esophageal carcinoma in the Eastern Asia. The need of early detection of precancerous neoplastic lesions and cancer has been necessitated due to the probability of progression to the advanced stage and its poor prognosis. In recent times, many endoscopic modalities have come into practice for early detection and treatment. Endoscopic radiofrequency ablation (RFA) has been recommended as an efficient therapy in treating the dysplastic mucosa in Barrett's esophagus (BE). Its potential in reversing neoplastic lesions in squamous epithelium has been gradually explored. This article is aimed at reviewing the current evidence regarding the use of RFA on esophageal squamous cell neoplasia.

The in vivo tissue effect of endoscopic balloon-based radiofrequency ablation in treating esophageal squamous cell neoplasia

Background

Endoscopic radiofrequency ablation (RFA) is a rapidly evolving therapeutic modality for early flat esophageal squamous cell neoplasms (ESCNs). However, the in vivo tissue effects of RFA on the esophageal wall are uncertain.

Methods

We prospectively enrolled eight patients with flat-type early ESCNs who were treated with balloon-based RFA. We evaluated the in vivo tissue effect on the esophagus using endoscopic ultrasound (EUS) and the histology of retrieved coagulum.

Results

The mean tumor length was 6.1 cm, and six of the eight patients achieved a complete response after primary RFA. Real-time evaluation of the tissue effect showed that the mucosa and submucosal layer were more edematous and thicker after RFA than before the procedure (mean 4.89 vs. 2.04 mm, p<.001), suggesting that the thermal effect of RFA may injure the submucosa. Histological evaluation of retrieved coagulum showed a severe cauterization (burning) effect with extensive cell necrosis; however, four cases had some residual viable neoplastic cells. Even though there were viable cells in the sloughed coagulum, half of the patients still achieved complete remission after RFA.

Conclusions

Our findings suggest that the thermal effect of RFA may injure the submucosal layer and enable neoplastic epithelium to slough off without "burning."

Evaluation of a novel cryoballoon swipe ablation system in bench, porcine, and human esophagus models

Current ablation devices for dysplastic Barrett's esophagus are effective but have significant limitations. This pilot study aims to evaluate the safety, feasibility, and dose response of a novel cryoballoon swipe ablation system (CbSAS) in three experimental in vitro and in vivo models. CbSAS is a through-the-scope compliant balloon that is simultaneously inflated and cooled by liquid nitrous oxide delivered from a disposable handheld unit. When the cryogen is applied through a special diffuser it covers a 90° section of the circumference of the esophagus for 3 cm length. Doses range from 0.9 to 0.5 mm/second. (1) Bench model: The fixture consisted of an 'esophagus-like' tube lined with agar at 37°C to create an inner diameter of 20 or 30 mm, within which thermocouples were embedded. (2) In vivo porcine esophagus: CbSAS ablations were performed in animals that were euthanized and histological assessments of depth and percentage of esophageal mucosa successfully ablated were done. (3) In vivo, pre-esophagectomy human esophagus. After CbSAS ablations, histological assessments were performed (at 0, 4, and 28 days) to assess the depth and percentage of ablated mucosa. As outcomes, we assessed the safety and tolerability (pain and serious, device-related adverse events); efficacy (depth and uniformity) of ablation; and device performance (ease of deployment and device malfunction). In the bench model, during CbSAS, thermocouples measured minimal temperatures of -40 to -48 °C at all doses. In the porcine model, maximal effect on the mucosa was reached with a dose of 0.8 mm/second that extended to superficial submucosa, while 0.5 mm/second extended through the submucosa. All animals tolerated the treatments and, regardless of ablation dose, continued oral intake and gained weight. In the human model, six patients (5 male, 1 female, mean age 68) tolerated the procedure without adverse events. CbSAS was simple to operate, and balloon contact with tissue was easily and uniformly maintained. The maximal effect on the mucosa is achieved with a 0.8 mm/second dose. We concluded that the CbSAS device enables uniform 3 cm long, quarter-circumferential mucosal ablation in a one-step process by using a novel, through-the-scope balloon. The CbSAS delivers predictable ablation with mucosal and limited submucosal necrosis in bench, animal, and human esophagus. Because of its ease of use, this new device merits further clinical study in the treatment of patients with dysplastic Barrett's esophagus.

Balloon-based esophageal cryoablation with a novel focal ablation device: dose-finding and safety in porcine and human models

The new Cryoballoon Focal Ablation System (CbFAS), a through-the-scope catheter with battery-powered handle that delivers cryogenic fluid into an inflated balloon, differs from current cryotherapy methods used for treatment of Barrett's epithelium. In this dose-finding study, short- and long-term histopathological effects and safety of the CbFAS were evaluated. Cryoablations with (supra)therapeutic durations (4-24 seconds) were performed in pigs that survived for 12 or 48 hours or 4 or 28 days. Next, cryoablations (durations based on animal data) were performed in normal mucosa of esophageal cancer patients scheduled to undergo esophagectomy. The outcome parameters, the occurrence of any bleeding or perforation, the histological presence of edema, inflammation, and necrosis throughout the esophageal wall layers, were evaluated. A total of 60 cryoablations were performed in 11 pigs. 48 hour cryoablations with therapeutic durations (4-10 seconds) resulted in edema/inflammation as deep as the serosa and necrosis ranging from submucosa to serosa with a median depth of 3.2 mm. In 4 day cryoablations this was in the serosa, and muscularis tunica to serosa at a median depth of 4.5 mm, respectively. No necrosis or inflammation remained after 28 days, not even after supratherapeutic cryoablation (12-24 seconds). No acute or delayed bleeding or perforation was observed. Next, eight 6-second cryoablations were performed in four patients. Direct postablation mucosal necrosis was observed; after 4 days necrosis and inflammation was limited to the submucosa. CbFAS cryoablation penetrates deeply into the esophageal wall layers resulting in severe early ablation. After 4 weeks, little injury and no fibrosis remain, even after supratherapeutic durations of administration, suggesting that CbFAS combines deep ablation with a potentially favorable safety profile.

Predictors for postoperative esophageal stricture after balloon-based radiofrequency ablation for early esophageal squamous neoplasia: a multicenter validation study

BACKGROUND

Endoscopic radiofrequency ablation (RFA) is a rapidly evolving therapeutic modality for early flat esophageal squamous cell neoplasms (ESCNs), but the risk factors for postoperative stricture have not been elucidated. The objective of this study was to identify and validate a predictor for post-RFA stenosis.

METHODS

We consecutively enrolled patients with flat-type 'large' (length no less than 3 cm extending no less than half the circumference of the esophagus), early ESCNs, treated with balloon-based RFA (12 J/cm(2)-clean-12 J/cm(2) regimen). The tumor and technical factors for postoperative stricture were investigated and we validated the results externally with a society-based multicenter cohort using the same ablation regimen.

RESULTS

A total of 51 patients were enrolled (30 in the development set and 21 in the validation set). The complete remission rate at 12 months was 93%, and the rates of perforation and postoperative stenosis were 0% and 17%, respectively. Patients with post-RFA stenosis had a significantly larger longitudinal tumor size (mean 115 versus 61 mm, p = 0.003). There were no significant differences in age, body mass index, tumor circumferential extension, pretreatment histological grade, treatment efficacy or size of balloon catheter between the groups with or without stenosis. The optimal cut-off value was set as 9 cm to predict post-RFA stenosis by receiver operating characteristic curve [area under curve (AUC) = 0.881], which was then confirmed to be a reliable predictor by multivariate analysis (odds ratio, 12.7, 95% confidence interval, 1.18-136.28, p = 0.03) and have a good predictive performance in the validation set (AUC = 0.876).

CONCLUSIONS

The most frequent adverse event of RFA was esophageal stenosis, for which the longitudinal tumor size was a significant predictive factor. Early intervention or prevention for stricture should be applied for those with long segment (⩾9 cm) ESCNs.

Radiofrequency Ablation Versus Endoscopic Submucosal Dissection in Treating Large Early Esophageal Squamous Cell Neoplasia

Radiofrequency ablation (RFA) and endoscopic submucosal dissection (ESD) can potentially be applied for early esophageal squamous cell neoplasia (ESCN); however, no study has directly compared these 2 modalities.We retrospectively enrolled the patients with flat-type "large" (length ≥3 cm extending ≥1/2 of the circumference of esophagus) early ESCNs treated endoscopically. The main outcome measurements were complete response at 12 months, and adverse events.Of a total of 65 patients, 18 were treated with RFA and 47 with ESD. The procedure time of RFA was significantly shorter than that of ESD (126.6 vs 34.8 min; P < 0.001). The complete resection rate of ESD and complete response rate after primary RFA were 89.3% and 77.8%, respectively. Based on the histological evaluation of the post-ESD specimens showed 14 of 47 (29.8%) had histological upstaging compared with the pre-ESD biopsies, and 4 of them had lymphovascular invasion requiring chemoradiation or surgery. After additional therapy for residual lesions, 46 (97.9%) patients in the ESD group and 17 (94.4%) patients in the RFA group achieved a complete response at 12 months. Four patients (8.5%) developed major procedure-related adverse events in the ESD group, but none in the RFA group. In patients with lesions occupying more than 3/4 of the circumference, a significantly higher risk of esophageal stenosis was noted in the ESD group compared with RFA group (83% vs 27%, P = 0.01), which required more sessions of dilatation to resolve the symptoms (median, 13 vs 3, P = 0.04). There were no procedure-related mortality or neoplastic progression in either group; however, 1 patient who received ESD and 1 who received RFA developed local recurrence during a median follow-up period of 32.4 (range, 13-68) and 18.0 (range, 13-41) months, respectively.RFA and ESD are equally effective in the short-term treatment of early flat large ESCNs; however, more adverse events occur with ESD, especially in lesions extending more than 3/4 of the circumference. RFA does not allow for pathology to evaluate the curability after ablation, and thus currently the use for invasive ESCNs should be conservative until longer follow-up studies are available.

Optimization of the generator settings for endobiliary radiofrequency ablation

AIM: To determine the optimal generator settings for endobiliary radiofrequency ablation.

METHODS: Endobiliary radiofrequency ablation was performed in live swine on the ampulla of Vater, the common bile duct and in the hepatic parenchyma. Radiofrequency ablation time, “effect”, and power were allowed to vary. The animals were sacrificed two hours after the procedure. Histopathological assessment of the depth of the thermal lesions was performed.

RESULTS: Twenty-five radiofrequency bursts were applied in three swine. In the ampulla of Vater (n = 3), necrosis of the duodenal wall was observed starting with an effect set at 8, power output set at 10 W, and a 30 s shot duration, whereas superficial mucosal damage of up to 350 μm in depth was recorded for an effect set at 8, power output set at 6 W and a 30 s shot duration. In the common bile duct (n = 4), a 1070 μm, safe and efficient ablation was obtained for an effect set at 8, a power output of 8 W, and an ablation time of 30 s. Within the hepatic parenchyma (n = 18), the depth of tissue damage varied from 1620 μm (effect = 8, power = 10 W, ablation time = 15 s) to 4480 μm (effect = 8, power = 8 W, ablation time = 90 s).

CONCLUSION: The duration of the catheter application appeared to be the most important parameter influencing the depth of the thermal injury during endobiliary radiofrequency ablation. In healthy swine, the currently recommended settings of the generator may induce severe, supratherapeutic tissue damage in the biliary tree, especially in the high-risk area of the ampulla of Vater.

Systematic review: the prevention of oesophageal stricture after endoscopic resection

BACKGROUND

Extensive endoscopic resections for the treatment of early oesophageal neoplasia can result in fibro-inflammatory strictures that require repeated interventions, which significantly alter the patients' quality of life.

AIMS

To review current evidence about the prevention of oesophageal strictures following endoscopic resections.

METHODS

Systematic search of PubMed and Embase from inception to March 2015 using appropriate keywords. All original publications in English were included, and articles on the treatment of oesophageal stricture were excluded.

RESULTS

Of the 461 hits, 62 studies were included in the analysis. Among the wound-protective strategies, polyglycolic acid sheets showed the most convincing evidence with a 37.5% stricture rate and excellent safety. Regenerative medicine, using cell sheets of autologous keratinocytes, resulted in a 25% stricture rate, although with cost and availability concerns. Among anti-proliferative treatment modalities, steroid treatment, either endoscopically injected triamcinolone in the resection wound or orally administered prednisolone, proved effective with an overall stricture rate of 13.5%, with safety concerns regarding late oesophageal perforations and infectious morbidity. Among mechanical treatment options, poorly effective and high-risk preventive balloon dilation tend to be replaced by prophylactic covered stent, with 18-28% stricture rates.

CONCLUSIONS

Although oral or locally injected steroids are promising options, no currently available technique is sufficiently efficient and devoid of significant safety concerns to recommend its routine use for the prevention of strictures after extensive endoscopic resection. Improving our knowledge in the mechanisms of oesophageal wound healing will guide the development of novel methods for stricture prevention.