Laparoscopic radioisotope-guided sentinel lymph node mapping and excision of the rectum—an experimental study

Abstract

Patients with a low-risk T1 rectal carcinoma can undergo the therapy of a local excision. In these patients the lymph node (LN) status remains unknown. There is a potential risk of up to 7% for nodal metastasis. To investigate the possibility of using the sentinel lymph node (SLN) concept, an experimental study on pigs was undertaken. The objective was to laparoscopically identify and extract SLNs from the rectum using a radioisotope (RI). The experiment was conducted in 30 pigs, since the sample size calculation indicated that with 30 animals a two-sided 95% confidence interval for a single proportion using the large sample normal approximation would extend at most 0.107 from the observed proportion of 0.9. One milliliter of a mixture of the RI Technetium 99 m (Tc99 m) and patent blue V dye was administered in the rectum endoscopically and after the lapse of 1 h, we laparoscopically identified and excised all SLNs using a laparoscopic gamma camera probe. We found in all operated pigs (n = 30) at least one SLN (lymph node with highest measured counts per second (cps)). In mean we detected 1.6 SLN (range one to three SLNs). In 28 cases, the SLN concept was successful. Sensitivity for detecting SLNs was 93% (n = 28/30), the probe count rate ranged from 600-10,000 cps with a median of 3,800. Minimal invasive mapping and excision of SLN of the rectum using a RI is feasible. The sensitivity for detecting SLN was high (93%). The application of this procedure on humans seems to be possible.