Nucleotide-guided Mesorectal Excision (ngme) During Transanal Endoscopic Microsurgery (tem) for Rectal Cancer: Preliminary Study

Introduction: TEM is used for local excision of T1N0 rectal cancer and it has been proposed to treat selected T2-T3 N0 cases after neoadjuvant radiochemotherapy. Standard TEM usually removes few mesorectal lymphnodes immediately adjacent to the tumor, which may leave the histopathological N parameter undefined. This may be a criticism to the use of TEM to treat T2-T3 patients. Aim is to evaluate the role of NGME during TEM to increase the lymphnode harvest and to improve staging. Methods: From September 2005 to August 2007, 18 patients (pts) (12 males, 6 females, mean age 69 years, range 37-87 years) underwent TEM with NGME for rectal adenocarcinoma. Pre-treatment staging was: T1 N0 11 pts, T2 N0 3 pts, T3 N0 1 pts, T3 N1 3 pts. Pre-treatment median tumor size was 3 cm (range 1-8 cm). Seven pts underwent neoadjuvant radiochemotherapy, with tumor downsizing in all of them. At surgery, 99m-Technetium-marked nanocolloid was injected in the peritumoral submucosa 45 minutes before excision. The area of excision was explored with a transanal probe in order to detect any residual radioactivity area, which was marked with metal clips and excised by TEM. The procedure was repeated until no residual radioactivity was detected. Hot lymphnodes were processed by immuno-histochemistry to detect micrometastases. Results: Median tumor distance (distal margin) from the anal verge was 5.5 cm (range 3-15 cm). Mean operative time was 92.6 min (range 50-300 min). Median time to passage of stool was 2 days (range 1-4 days) and median hospital stay was 5.5 days (range 2-13 days). Morbidity included fever and pain in 2 pts each, and soiling in 1 case. Mortality was nil. With improving experience in radioguided surgery the mesorectal lymphnode harvest has increased from 0 to 10. No micrometastases were observed. Final pathology report was Tis No 1 pt, T1 N0 9 pts, T2 N0 5 pts, T3 N0 2 pts, T2 N1 1 pt. The latter patient underwent low anterior rectal resection with total mesorectal excision (TME), and pathological classification was N0. At mean follow up of 12.8 months (range 1-24 months) 17 pts are alive and disease-free. One patient died from unrelated causes 2 months after excision of Tis N0 rectal cancer. Conclusions: The described technique is unique. NGME during TEM increases the lymphnode harvest and it holds promise to improve the accuracy of staging after TEM, although no conclusive data can be drawn from the present study.

Session: Poster

Program Number: P123

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