Self-expandable covered metallic esophageal stent impregnated with beta-emitting radionuclide: an experimental study in canine esophagus.
OBJECTIVE
A specially designed self-expandable covered metallic stent impregnated with the beta-emitting radioisotope 166Ho (166Ho, energy: 1.85 and 1.76 MeV, T12: 26.8 h) was developed at our institute for the purpose of intraluminal palliative brachytherapy, as well as for treating malignant esophageal stricture and swallowing difficulty. The aim of this study was to evaluate the tissue response to brachytherapy and the safety of the radioactive metallic stent with regard to the normal canine esophagus before clinical application.


METHODS
166Ho was impregnated into the polyurethane membrane (50 micron thickness) covering the outer surface of a self-expandable metallic stent (diameter, 18 mm; length, 40 mm). Stents with radioactivity 4.0-7.8 mCi (Group A, n = 15), 1.0-1.8 mCi (Group B, n = 5), and 0.5-0.7 mCi (Group C, n = 5) were placed in the esophagi of 25 healthy beagle dogs, and the stents were tightly anchored surgically to prevent migration. The estimated radiation dose calculated by Monte Carlo simulation was 194-383 Gy in Group A, 48-90 Gy in Group B, and 23-32 Gy in Group C. The dogs were killed 8-12 weeks after insertion of the stents, and histologic examinations of the esophageal walls were performed.


RESULTS
In Group A, 3 of 15 dogs died of wound infection, so specimens were obtained from only 12 dogs; all 12 cases showed esophageal stricture with mucosal ulceration. Microscopically, severe fibrosis and degeneration of the muscular propria were found in 3 dogs, complete fibrosis of the entire esophageal wall was found in 7 dogs, and esophageal fibrosis with radiation damage within periesophageal soft tissue was found in 2 dogs. However, esophageal perforation did not develop, despite extremely high radiation doses. In Group B, glandular atrophy and submucosal fibrosis were found, but the muscular layer was intact. In Group C, no histologic change was found in 3 dogs, but submucosal inflammation and glandular atrophy with intact mucosa were found in 2 dogs.


CONCLUSIONS
A radioactive, self-expandable covered metallic stent can be used as an alternative therapeutic modality for the palliative treatment of malignant esophageal stricture.
Won
Je Hwan
JH
Department of Diagnostic Radiology, College of Medicine, Yonsei University, Seoul, South Korea.
Lee
Jong Doo
JD
Wang
Hee Jung
HJ
Kim
Gui-Eon
GE
Kim
Bong Wan
BW
Yim
Hyunee
H
Han
Sang Keon
SK
Park
Chan H
CH
Joh
Chul Woo
CW
Kim
Kyung-Hwa
KH
Park
Kyung Bae
KB
Shin
Kyong-Min
KM
D000818:Animals; D001918:Brachytherapy / Q000379:methods*; D004285:Dogs; D004847:Epithelial Cells / Q000473:pathology / Q000528:radiation effects; D004938:Esophageal Neoplasms / Q000532:radiotherapy*; D004947:Esophagus / Q000473:pathology / Q000528:radiation effects; D005471:Fluoroscopy; D006695:Holmium / Q000627:therapeutic use*; D009092:Mucous Membrane / Q000473:pathology / Q000528:radiation effects; D011868:Radioisotopes / Q000627:therapeutic use*; D011874:Radiometry
D011868:Radioisotopes; D006695:Holmium