Endoscopic Nd:YAG treatment of superficial gastric carcinoma: experience in 18 Western inoperable patients

Modular laser-based endoluminal ablation of the gastrointestinal tract: in vivo dose-effect evaluation and predictive numerical model

BACKGROUND

Endoscopic submucosal dissection allows for "en bloc" removal of early gastrointestinal neoplasms. However, it is technically demanding and time-consuming. Alternatives could rely on energy-based techniques. We aimed to evaluate a predictive numerical model of thermal damage to preoperatively define optimal laser settings allowing for a controlled ablation down to the submucosa, and the ability of confocal endomicroscopy to provide damage information.

MATERIALS AND METHODS

A Nd:YAG laser was applied onto the gastric mucosa of 21 Wistar rats on 10 spots (total 210). Power settings ranging from 0.5 to 2.5W were applied during 1-12 s, with a consequent energy delivery varying from 0.5 to 30 J. Out of the 210 samples, a total of 1050 hematoxilin-eosin stained slides were obtained. To evaluate thermal injury, the ratio between the damage depth (DD) over the mucosa and the submucosa thickness (T) was calculated. Effective and safe ablation was considered for a DD/T ratio ≤ 1 (only mucosal and submucosal damage). Confocal endomicroscopy was performed before and after ablation. A numerical model, using human physical properties, was developed to predict thermal damage.

RESULTS

No full-thickness perforations were detected. On histology, the DD/T ratio at 0.5 J was 0.57 ± 0.21, significantly lower when compared to energies ranging from 15 J (a DD/T ratio = 1.2 ± 0.3; p < 0.001) until 30 J (a DD/T ratio = 1.33 ± 0.31; p < 0.001). Safe mucosal and submucosal ablations were achieved applying energy between 4 and 12 J, never impairing the muscularis propria. Confocal endomicroscopy showed a distorted gland architecture. The predicted damage depth demonstrated a significant positive linear correlation with the experimental data (Pearson's r 0.85; 95% CI 0.66-0.94).

CONCLUSIONS

Low-power settings achieved effective and safe mucosal and submucosal ablation. The numerical model allowed for an accurate prediction of the ablated layers. Confocal endomicroscopy provided real-time thermal damage visualization. Further studies on larger animal models are required.

Effects of Nd:YAG laser for the controlled and localized treatment of early gastrointestinal tumors: Preliminary in vivo study

Endoscopic submucosal dissection (ESD) is a minimally invasive technique allowing for the removal of early gastrointestinal (GI) tumors, widely considered as a valid alternative to conventional surgery. However, ESD is technically demanding, and potentially severe complications, such as bleeding and perforation, may occur. Energy-based techniques (e.g., radiofrequency ablation) might offer a potential alternative to ESD. However, their use mandates the ability to predict the damage induced and to identify a "signature" of the complete ablation, without the need for a physical specimen. Ideally, an energy-based procedure should be tunable in order to limit the ablation to the superficial layers, namely mucosa (M) and submucosa (SM), without injuring the muscularis propria (MP), thereby minimizing GI perforation. This experimental study aims to investigate thermal damage induced by Nd:YAG laser on the gastric wall, at different laser settings such as power (P) and time (t). Laser ablation was performed on the stomach wall of 6 Wistar rats. Two powers (2.5W and 1.0W) and 3 exposure times (12s, 6s and 2s) were tested, for a total of 30 ablations. Histological analysis allowed to assess thermal damage, in terms of damage depth (DD) and identification of involved layers. The ratio (R) between DD and the total depth (TD) of target layers (M+SM) was used as an index to evaluate the effectiveness of laser settings. At P=2.5W, MP was damaged (R>1) in the majority of cases (11/15). At P=1.0W, MP was preserved in all tests (R<;1), and rarely (4/15) did the damage reach the whole SM (R=1). Histopathological analysis evidenced that tissue damage was strongly related to the variable tissue thickness. These preliminary results seem to support the fact that endoscopic tunable laser ablation is feasible with a consistent damage/power correlation. Further tests are required to optimize the settings for applications on early GI tumors.

Outcome of photodynamic therapy for early esophageal cancer

BACKGROUND/AIMS

Endoscopic treatment as an alternative to surgery has become increasingly popular for improving the quality of life. Although photodynamic therapy (PDT) has been used for the endoscopic treatment of digestive cancer, its curative efficacy remains unclear. We evaluated the curative efficacy of PDT in superficial esophageal cancer in inoperable patients.

METHODS

Ten male patients with histologically proven early esophageal cancer (surgery was contraindicated for age > 80 years, surgery was contraindicated, Karnofsky performance status of at least 30%, or refusal of surgery) were intravenously injected with a hematoporphyrin derivative (2 mg/kg), and PDT was performed 48 h later. The response to treatment was assessed by gastroscopy with biopsies.

RESULTS

The mean follow-up period was 27.6 months (range, 9.6-58.7 months). Endoscopic ultrasonography revealed that all ten cases were at tumor stage T1. Complete remission (CR) to initial and subsequent PDT was observed in all patients. For the CR cases, the recurrence rate was 10% (1/10) and the time from initial PDT to recurrence was 9.6 months.

CONCLUSIONS

For patients in whom surgery is risky or refused, PDT may represent an acceptable alternative treatment modality, especially for superficial esophageal cancer without lymph node metastasis. However, a study involving long-term follow-up in a large population is needed for confirmation.

Argon plasma coagulation in Barrett's esophagus

Despite the availability of many clinical trials, there is no evidence that APC has any role in the management of Barrett's esophagus. Ablation therapy is not indicated for nondysplastic Barrett's esophagus (and this is true, whatever the technique used), and it should not be performed outside of a carefully designed and approved clinical trial. Indeed, these patients have a low risk of cancer, and there is no evidence that Barrett's esophagus ablation will be of any benefit for these patients. In some cases, APC could be of some help, especially for treating short segments of dysplastic Barrett's esophagus. In this field, however, it competes with the growing indication of mucosectomy, which clearly offers advantages in terms of treatment's quality control assessment.

Fluorescein electronic endoscopy: a novel method for detection of early stage gastric cancer not evident to routine endoscopy

BACKGROUND

Fluorescence endoscopy with fluorescein sodium in the stomach was evaluated by using a newly developed fluorescence electronic endoscopic system.

METHODS

Sixteen patients with early stage gastric cancer diagnosed by white light endoscopy and chromoendoscopy underwent fluorescein electronic endoscopy before surgery. The resection specimens underwent thorough histopathologic evaluation.

RESULTS

About 10 seconds after intravenous injection of fluorescein, fluorescence appeared and immediately spread throughout the gastric surface. A few minutes later, differentiated early stage gastric cancers with more abundant stroma than surrounding normal mucosa exhibited significantly stronger fluorescence, and those with less stroma exhibited weaker fluorescence than the surrounding normal mucosa. Undifferentiated early stage gastric cancers, in which the stroma became wider because foveolae were collapsed from malignant invasion, expressed stronger fluorescence intensity. In all cases, the borders of early stage gastric cancers were clearly demonstrated. Among the 16 patients, 6 accompanying flat lesions and 1 tiny lesion not evident by routine endoscopy were detected. The extent of the cancers, as determined by fluorescence endoscopy, were similar to those determined histopathologically.

CONCLUSIONS

Fluorescein electronic endoscopy is useful in determining the extent within the mucosa of gastric cancers when this is obscure by standard endoscopic observation, and for detecting extremely early stage cancer that is not evident by conventional endoscopic observation.

Hydrogastric sonography in the preoperative staging of gastric cancer

PURPOSE

Depth of wall invasion is the main prognostic factor in gastric cancer. We studied the utility of hydrogastric sonography in the evaluation of transmural infiltration by gastric cancer.

METHODS

Thirty-seven patients with gastric adenocarcinoma were examined before surgery with a 5-MHz probe after the ingestion of 100-400 ml of water (mean, 330 ml). Sonographic results were compared with pathologic classifications obtained after surgery.

RESULTS

Of the 37 tumors, 15 were found at surgery to be in the antrum, 10 were in the gastric body, 5 were proximal, and 7 were diffuse. After surgery, tumors were classified as follows: 2 (5%) T1, 4 (11%) T2, 15 (41%) T3, and 16 (43%) T4. Hydrogastric sonography correctly classified 30 (81%) of the 37 tumors. Sonography was correct for 2 (100%) of the 2 T1 tumors, 2 (50%) of the 4 T2 tumors, 13 (87%) of the 15 T3 tumors, and 13 (81%) of the 16 T4 tumors. Five sonographic errors were due to understaging and 4 to overstaging. With regard to tumor site, sonographic results were correct for 4 (57%) of the 7 diffuse tumors, 3 (60%) of the 5 proximal tumors, 9 (90%) of the 10 gastric body tumors, and 14 (93%) of the 15 antral tumors.

CONCLUSIONS

Hydrogastric sonography is useful for preoperative evaluation of transmural infiltration by gastric cancers, particularly tumors in the antrum or gastric body.

Gastric Cancer

The best treatment for gastric cancer remains early detection and prompt surgical removal. Currently, the majority of gastric carcinomas diagnosed in western centers are late-stage tumors with poor prognoses. Endoscopic ultrasound and diagnostic laparoscopy aid our ability to accurately stage patients with gastric cancers, and may prevent unnecessary laparotomies in asymptomatic patients. While extended lymphadenectomy is the standard approach in Japanese centers, the utility of this procedure in improving long-term survival has yet to be proved in prospective, randomized trials. Accurate staging of patients preoperatively and selected multidisciplinary approaches to individual patients may eventually lead to improvements in survival for patients with gastric cancer.