Use of lasers in Barrett's esophagus

Guide mapping for effective superficial photothermal coagulation of the esophagus using computer simulations with ex vivo sheep model validation study

OBJECTIVES

The transfer and widespread acceptance of laser-induced thermal therapy into gastroenterology remain a topic of interest. However, a practical approach to the quantitative effect of photothermal injury in the esophagus needs further investigation. Here, we aim to perform computer simulations that simulate laser scanning and calculate the laser-induced thermal damage area. The simulation engine offers the results in a guide map for laser coagulation with a well-confined therapeutic area according to laser irradiance and surface scanning speed. The study also presents validation experiments that include histology analyses in an ex vivo sheep esophagus model.

METHODS

The simulation engine was developed based on the Monte-Carlo method and the Arrhenius damage integral. The computational model mimicked laser scanning by shifting the position of the calculated heat source in the grating system along the axis to be scanned. The performance of the simulations was tested in an ex vivo sheep esophagus model at a laser wavelength of 1505 nm. Histological analysis, hematoxylin-eosin staining, light microscope imaging, and block-face scanning electron microscopy were used to assess thermal damage to the tissue model.

RESULTS

The developed simulation engine estimated the photothermal coagulation area for a surface scanning speed range of 0.5-8 mm/second and laser power of up to 0.5 W at a 0.9-nm laser diameter in a tissue model with a volume of 4 × 4 × 4 mm³ . For example, the optimum laser irradiation for effective photothermal coagulation in the mucosa and superficial submucosa depths was estimated to be between 16.4 and 31.8 W/cm² , 23.2 and 38.1 W/cm² at 0.5 and 1 mm/second, respectively. The computational results, summarized as a guide map, were directly compared with the results of ex vivo tissue experiments. In addition, it was pointed out that the comparative theoretical and experimental data overlap significantly in terms of energy density.

CONCLUSIONS

Our results suggest that the developed simulation approach could be a seed algorithm for further preclinical and clinical trials and a complementary tool to the laser-induced photothermal coagulation technique for superficial treatments in the gastrointestinal tract. In future preclinical studies, it is thought that the simulation engine can be enriched by combining it with an in vivo model for different laser wavelengths.

An analysis of esophagectomy and other techniques in the management of high-grade dysplasia of Barrett's esophagus

Barrett's esophageal (BE) metaplasia is a premalignant condition of the distal esophagus that develops as a consequence of gastroesophageal reflux disease. The progression to carcinogenesis results from progressive dysplastic changes of the metaplastic epithelium through low-grade and then high-grade dysplasia (HGD) to eventually adenocarcinoma of the esophagus. The management of HGD is controversial with proponents for each of the three major management strategies: endoscopic surveillance, endoscopic ablative therapies, and esophagectomy. The aim of the study was to define and discuss the various management strategies of HGD arising from BE metaplasia. There is a paucity of randomized controlled data from which to draw definitive conclusions. All strategies for the management of HGD are reasonable options and are complimentary. BE with HGD is a malignant lesion. A multidisciplinary approach individualizing therapy should be undertaken when possible. Esophageal resection should be reserved for otherwise healthy patients. Endoscopic techniques are viable alternatives to surgery.

Systematic four-quadrant biopsy detects Barrett's dysplasia in more patients than nonsystematic biopsy

AIMS

To compare detection of Barrett's dysplasia and adenocarcinoma by systematic versus nonsystematic surveillance biopsy protocols.

METHODS

Upper GI consultation and open-access endoscopy are provided jointly at Glasgow Royal Infirmary by medical and surgical teams. The surgical team adopted annual systematic four-quadrant biopsy Barrett's surveillance in 1995. The medical team continued annual Barrett's surveillance with nonsystematic biopsy until 2004. We compare detection of Barrett's dysplasia and esophageal adenocarcinoma in unselected patients by these two biopsy strategies over 10 yr. All patients had > or = 3 cm Barrett's esophagus and histological proof of intestinal metaplasia. Patients referred for dysplasia management or with prevalent adenocarcinoma were excluded. Cohort A (N = 180) had four-quadrant biopsy every 2 cm while cohort B (N = 182) had nonsystematic biopsies.

RESULTS

Cohort A versus cohort B: Median number of biopsies per endoscopy: 16 versus 4. Prevalence of low-grade dysplasia (per patient): 18.9% versus 1.6% (P << 0.001). Prevalence of high-grade dysplasia: 2.8% versus 0% (P = 0.03). Incidence of low-grade dysplasia: 2.2% versus 6.6% (NS). Incidence of high-grade dysplasia: 2.8% versus 0% (P = 0.03). Nine cohort A patients (total 5%, 1.4% per patient-year) were treated for HGD (eight endoscopically, one by esophagectomy). Two had intramucosal adenocarcinoma. No cohort A patient developed advanced cancer but three cohort B patients developed and died of invasive Barrett's adenocarcinoma (0.6% per patient-year).

CONCLUSIONS

Patient age, gender, Barrett's segment length, and follow-up were similar (though not identical) in both cohorts, but confounding seems unlikely to account for a 13-fold difference in detection of prevalent dysplasia between the two groups. Our data support the hypothesis that systematic four-quadrant biopsy is considerably more effective than nonsystematic biopsy sampling in detecting Barrett's dysplasia and early adenocarcinoma. Greater biopsy numbers and the systematic pattern of biopsy taking may both contribute to this greater effectiveness.