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

Abstract

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. 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. (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. 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.