Knife-assisted full-thickness resection guided by the pocket-detection method for posterior deeply invasive rectal cancer: A novel endoscopic approach (with video).

Local full-thickness resection techniques for rectal cancer are limited by lesion size, location, or poor margin delineation. We aimed to evaluate the feasibility of endoscopic knife-assisted full-thickness resection (kFTR) guided by the pocket-detection method (PDM) for deeply invasive rectal cancer. Consecutive posterior-lateral rectal lesions suspected of deep submucosal invasion treated at a tertiary care center from February to October 2024 were retrospectively included. kFTR guided by PDM involved creating a submucosal pocket to detect and isolate the suspected invasive component (muscle-retracting sign), followed by muscularis propria incision and full-thickness resection. Technical success, accuracy of detecting deep submucosal invasion, and en-bloc resection rates were 100%. The median procedure time was 141.5 [IQR 123.7-179.5] minutes and the median hospitalization was 1 [IQR 1-7] day. No adverse events occurred. Histopathology showed R1-vertical margin in patient 1 (pT2 adenocarcinoma) and R0 resection in patients 2, 3, and 4 (pT1bsm3) after refinement of the procedure to include a ≥3 mm muscularis propria margin around the suspected invasive component. There was no recurrence at the first endoscopic follow-up of patients 1, 2, and 4. Patient 3 was sent to surgical low anterior resection due to multiple high-risk histological features. The previous kFTR did not impair surgery (no residual rectal carcinoma and 1/17 positive lymph nodes). Endoscopic kFTR guided by the PDM may be a feasible organ-preserving treatment for the detection and resection of deeply invasive posterior rectal cancer. Future studies are needed to ascertain whether rectal kFTR could represent a viable alternative to conventional surgical local excision techniques.