Background: Endoluminal locoregional resection (ELRR) by transanal endoscopic microsurgery (TEM) is an alternative treatment option for T1N0 rectal cancer and for selected patients with small T2N0 rectal cancer after neoadjuvant radiochemotherapy (n-RCT). The N parameter may remain undefined after transanal surgery. This study aimed to evaluate the role of a modified sentinel lymph node technique to improve N staging that the authors named "nucleotide-guided mesorectal excision" (NGME).
Methods: The study enrolled 41 patients (24 men and 17 women) with a mean age of 70.5 years. Preoperative staging identified dysplasia with no suspicion for cancer at imaging (n = 8), dysplasia with suspected malignancy at imaging (n = 15), no suspicion of malignancy at imaging after n-RCT (n = 2), cT1N0 (n = 6), cT2N0 (n = 6), cT3N0 (n = 3), and cT3N1 (n = 1). The patients underwent ELRR by TEM with NGME. Before surgery, 99m-technetium-marked nanocolloid was injected into the peritumoral submucosa. After resection, the residual defect was probed to detect residual radioactivity. If present, hot mesorectal fat was excised.
Results: With NGME, the mesorectal lymph node harvest increased from 0 to 10. Lymph nodes were isolated in the specimen or in hot mesorectal fat of 20 patients, 8 of whom had undergone n-RCT. The mean lymph node harvest was 2.75 ± 3.01 (range 1-10) in the irradiated patients and 2.91 ± 1.62 (range 1-6) in the nonirradiated patients (p = 0.87). The average number of lymph nodes in the irradiated patients was higher than in a previous historical series.
Conclusions: The use of NGME during ELRR by TEM increases the lymph node harvest and may improve staging accuracy after transanal surgery.