Detection of gastric and colonic sentinel nodes through endoscopic administration of 99mTc-DTPA-mannosyl-dextran in pigs.

UNLABELLED: The purpose of this study was to develop a method for the endoscopic administration of a radiopharmaceutical for sentinel node detection and to characterize its uptake by gastric and colonic sentinel nodes. (99m)Tc-Diethylenetriaminepentaacetic acid (DTPA)-mannosyl-dextran is a new radiotracer labeled with (99m)Tc and composed of multiple units of mannose attached to the polymeric backbone, dextran.

METHODS

Gastric and colonic lymph node detection was studied in 4 fasting and anesthetized pigs. A flexible video endoscope was inserted into the rectum and positioned in the lower colon or advanced down the esophagus into the stomach. A standard endoscopic sclerotherapy needle and sheath filled with 0.9% saline was then loaded with 0.2 mL of a 7.4-MBq 1:1 (v/v) mixture of isosulfan blue and (99m)Tc-DTPA-mannosyl-dextran (7.4 MBq, 0.3 nmol). The needle and sheath were passed through the biopsy channel, and the radiotracer/dye solution (0.1 mL) was injected in a tangential fashion into the submucosa. Within 5-10 min after injection, all radioactive or blue lymph nodes were excised, assayed for radioactivity, and noted for color. Distal lymph nodes were also excised, assayed, and noted for color.

RESULTS

(99m)Tc-DTPA-mannosyl-dextran uptake by colonic sentinel nodes (n = 4) ranged from 0.54% to 2.4% of the injected dose; all radioactive nodes were stained blue. The uptake for all (n = 3) distal nodes ranged from 0.001% to 0.005%, and none of these nodes were stained blue. Uptake by gastric sentinel nodes (n = 6) ranged from 0.13% to 4.50%; all radioactive nodes were stained blue. The range for distal nodes was 0.001% to 0.050%; no distal nodes were stained blue. In 2 pigs, each gastric injection produced 2 hot and blue lymph nodes.

CONCLUSION

Within 10 min of a gastric and colonic submucosal injection, (99m)Tc-DTPA-mannosyl-dextran demonstrated high sentinel node uptake and high concordance with isosulfan blue.