The short and long term effects of intraoperative electron beam radiotherapy (IORT) on thoracic organs after pneumonectomy an experimental study in the canine model.
OBJECTIVE
The tolerance of mediastinal structures and thoracic organs to intraoperative radiotherapy (IORT) was investigated in the canine model.


METHODS
Twenty-two adult beagles divided into three groups were subjected to a left pneumonectomy and IORT (10 MeV electrons) at doses of 20 Gy (n = 9), 25 Gy (n = 4), or 30 Gy (n = 9). Intraoperative electron beam radiotherapy was delivered through a 5 cm circular lucite cone encompassing a mediastinal field including the bronchial stump, aorta, esophagus, heart, phrenic nerve, contralateral hilar structures, and lung. Clinical monitoring was performed with regular chest X-ray, ECG, bronchoscopy, esofagoscopy, and fluoroscopy. From the different treatment dose groups, dogs were electively sacrificed at 1.5, 6, 12, and 72 months with complete autopsies.


RESULTS
There was no bronchial stump dehiscence or acute morbidity. Four dogs developed radiation induced esophagitis (18%), one in the 20 Gy IORT group (11%) and three in the 30 Gy IORT group (33%). There were six IORT related mortalities (27.5%), one esophagoaortic fistula (4.5%) and five bronchovascular fistulas (23%): two in the 20 Gy IORT group (22%), two in the 25 Gy IORT group (50%) and two in the 30 Gy IORT group (22%). Histopathological findings in uncomplicated follow-up showed marked myointimal fibrosis in the muscular arteries, submucosal fibrosis of the esophagus, and interstitial fibrosis of bronchial and lung tissue, especially in the higher dose group.


CONCLUSIONS
The mediastinal vascular, bronchial and esophageal structures are relatively sensitive to doses > 20Gy IORT. The IORT related morbidity found in this study may be lower when the current clinically used IORT doses of 10-15 Gy are applied. Further clinical application of IORT in the future treatment strategies for resectable nonsmall cell lung cancer may be worthwhile to investigate.
de Boer
W J
WJ
Department of Cardiothoracic Surgery, University Hospital, Groningen, The Netherlands. W.J.de.Boer@thorax.azg.nl
Mehta
D M
DM
Timens
W
W
Hoekstra
H J
HJ
D000818:Animals; D001013:Aorta, Thoracic / Q000528:radiation effects; D001980:Bronchi / Q000528:radiation effects; D003331:Coronary Vessels / Q000528:radiation effects; D004285:Dogs; D004583:Electrons; D004947:Esophagus / Q000528:radiation effects; D007430:Intraoperative Care; D008168:Lung / Q000528:radiation effects; D011013:Pneumonectomy; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000502:physiology*; D013909:Thorax / Q000473:pathology / Q000528:radiation effects*; D016896:Treatment Outcome; D014945:Wound Healing