Which adult patients with esophageal or proximal gastric subepithelial tumors ≤ 3 cm, without coagulopathy, extensive fibrosis, or prior radiation, are appropriate candidates for submucosal tunneling endoscopic resection (STER) and what are its contraindications?

Submucosal Tunneling Endoscopic Resection (STER)

STER is appropriate for adult patients with esophageal or proximal gastric subepithelial tumors ≤3 cm originating from the muscularis propria layer, particularly when located in anatomically challenging areas like the cardia or proximal gastric fundus where scope manipulation for standard ESD is difficult. 1

Ideal Candidate Characteristics

Anatomic Location

• Esophagus (any level, including proximal esophagus) 1, 2
• Gastric cardia and proximal fundus where ESD scope manipulation is technically challenging 1
• Selected gastric corpus and antrum locations accessible via straight-line endoscopic approach 1, 3
• Rectum (when accessible in straight line) 1

Tumor Size Criteria

• Optimal size: ≤3 cm - lesions larger than 3-4 cm are difficult to remove through the submucosal tunnel and may require conversion to exposed full-thickness resection 1
• The mean tumor size in successful STER series was 1.7-2.3 cm (range 1.0-5.0 cm) 1, 3
• One study suggests limiting lesion size to 30 mm in the axis perpendicular to cranio-caudal length on cross-sectional imaging 1

Layer of Origin

• Muscularis propria layer is the primary indication 1, 4
• Submucosal lesions can also be treated, though standard ESD may be preferred if muscularis propria is not involved 1

Absolute Contraindications

Patient-Related Factors

• Coagulopathy or uncorrectable bleeding disorders (implied from standard endoscopic resection contraindications) 1
• Inability to tolerate general anesthesia - STER requires general anesthesia with endotracheal intubation for optimal safety 1
• Hemodynamic instability that would prevent safe completion of the procedure 1

Lesion-Related Factors

• Extensive submucosal fibrosis - prevents adequate tunnel creation and dissection 1
• Prior radiation therapy to the treatment area - causes tissue fibrosis that impairs tunneling 1
• Compromised mucosal integrity overlying the lesion - prevents safe tunnel creation and closure 1
• Ulcerated or actively bleeding lesions - these typically require surgical resection 1
• Lesions >3-4 cm - technical limitation due to difficulty extracting large tumors through the tunnel 1

Anatomic Contraindications

• Duodenum - the intended perforation risk and difficulty with prompt closure can cause significant morbidity with early hemodynamic and respiratory instability 1
• Locations not accessible via straight-line endoscopic approach - tunneling becomes technically prohibitive 1

Technical Advantages Over Alternative Approaches

STER offers specific benefits compared to exposed endoscopic full-thickness resection:

• Non-exposed technique - avoids full-thickness perforation and peritoneal/mediastinal contamination 1
• Easier mucosal closure - closing the mucosal entry point is simpler than closing a large full-thickness defect 1
• Mucosal flap protection - minimizes extravasation of luminal contents during dissection 1
• Enhanced stability - the confined tunnel space provides scope stability and traction on the lesion 1
• Safer in esophagus - avoids the devastating consequences of esophageal perforation and leak 1

Expected Outcomes

Efficacy

• En bloc resection rate: 78.7-95% across multiple studies 1, 5, 4
• Complete (R0) resection rate: 97.1-100% 1, 3, 4
• Residual tumor rate: 1.1% even after piecemeal resection 5
• No recurrence reported during follow-up periods of 6-32 months 3, 5, 4

Safety Profile

• Overall complication rate: 6.95-21.3% 2, 5
• Air leakage (pneumothorax, subcutaneous emphysema, pneumomediastinum): 15% - all managed conservatively 1, 4
• Perforation rate: 5.6% 1
• All complications successfully managed with conservative treatment - no surgical intervention required 3, 2, 5, 4
• Mean hospital stay: 4-5.9 days 2, 4

Critical Pitfalls and Caveats

Operator Experience

• STER should be limited to endoscopists highly skilled in advanced tissue resection techniques, particularly those experienced with ESD or peroral endoscopic myotomy 1
• Experience with ESD or STER is currently limited to retrospective single-center studies or case series 1

Tumor Characteristics Affecting Outcomes

• Deeper muscularis propria involvement (70% complication rate) versus superficial MP layer (1.3% complication rate) significantly impacts safety 4
• Irregular tumor shape increases risk of piecemeal resection and complications 2
• Larger tumor size increases operation time and technical difficulty 2
• GISTs have higher complication rates (26.3%) compared to leiomyomas (4.6%) 4

Procedural Considerations

• General anesthesia with endotracheal intubation is mandatory for positive pressure ventilation to manage capnoperitoneum/capnomediastinum 1
• Carbon dioxide insufflation is required due to faster absorption and lower adverse event risk 1
• Prophylactic intravenous antibiotics should be administered given contamination risk 1
• Peritoneal decompression needles must be readily available for managing pneumoperitoneum 1

When to Avoid STER

• Gastric fundus locations not accessible in straight line - tunneling becomes extremely challenging despite being technically possible 1, 3
• Bulky lesions approaching 4 cm - high likelihood of requiring conversion to exposed EFTR for complete excision 1
• Extraluminal extension - these lesions require full-thickness resection techniques instead 1