title: How Sensitive Is the Upper Gastrointestinal Tract to 90Y Radioembolization? A Histologic and Dosimetric Analysis in a Porcine Model.
abstract: In90Y radioembolization, nontarget embolization to the stomach or small bowel can result in gastrointestinal injury, a rare but difficult to manage clinical complication. However, dosimetric thresholds for toxicity to these tissues from radioembolization have never been evaluated in a controlled setting. We performed an analysis of the effect of90Y radioembolization in a porcine model at different absorbed-dose endpoints.
  
  
  METHODS
  Six female pigs underwent transfemoral angiography and infusion of90Y-resin microspheres into arteries supplying part of the gastric wall. Esophagogastroduodenoscopy was performed after 4 wk to assess interim gastrointestinal health. Animals were monitored for side effects for 9 wk after90Y infusion, after which they were euthanized and their upper gastrointestinal tracts were excised for analysis. Histologic sections were used to map microsphere location, and a microdosimetric evaluation was performed to determine the absorbed-dose profile within the gastrointestinal wall.
  
  
  RESULTS
  90Y radioembolization dosages from 46.3 to 105.1 MBq were infused, resulting in average absorbed doses of between 35.5 and 91.9 Gy to the gastric wall. No animal exhibited any signs of pain or gastrointestinal distress through the duration of the study. Excised tissue showed 1-2 small (<3.0 cm2) healed or healing superficial gastric lesions in 5 of 6 animals. Histologic analysis demonstrated that lesion location was superficial to areas of abnormally high microsphere deposition. An analysis of microsphere deposition patterns within the gastrointestinal wall indicated a high preference for submucosal deposition. Dosimetric evaluation at the luminal mucosa performed on the basis of microscopic microsphere distribution confirmed that90Y dosimetry techniques conventionally used in hepatic dosimetry provide a first-order estimate of absorbed dose.
  
  
  CONCLUSIONS
  The upper gastrointestinal tract may be less sensitive to90Y radioembolization than previously thought. Lack of charged-particle equilibrium at the luminal mucosa may contribute to decreased toxicity of90Y radioembolization compared with external-beam radiation therapy in gastrointestinal tissue. Clinical examples of injury from90Y nontarget embolization have likely resulted from relatively large90Y activities being deposited in small tissue volumes, resulting in absorbed doses in excess of 100 Gy.
authors.affiliation: Department of Radiology, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee alexander.pasciak@gmail.com.|The Johns Hopkins Hospital, School of Medicine, Baltimore, Maryland.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Pasciak
authors.affiliation: Department of Pathology, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee.
authors.forename: Laurentia
authors.initials: L
authors.lastname: Nodit
authors.affiliation: Department of Radiology, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee.|Department of Radiology, The Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Austin C
authors.initials: AC
authors.lastname: Bourgeois
authors.affiliation: Interventional Radiology, Prescott Radiologists, Prescott, Arizona.
authors.forename: Ben E
authors.initials: BE
authors.lastname: Paxton
authors.affiliation: Office of Lab Animal Care, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee.
authors.forename: Patricia N
authors.initials: PN
authors.lastname: Coan
authors.affiliation: Department of Pathology, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Clark
authors.affiliation: Department of Small Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee.
authors.forename: M Katherine
authors.initials: MK
authors.lastname: Tolbert
authors.affiliation: Office of Lab Animal Care, University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee.
authors.forename: Joleen K
authors.initials: JK
authors.lastname: Adams
authors.affiliation: Interventional Radiology, Piedmont Radiology, Atlanta, Georgia; and.|Interventional Radiology, Vanderbilt School of Medicine, Nashville, Tennessee.
authors.forename: Aravind
authors.initials: A
authors.lastname: Arepally
authors.affiliation: Department of Radiology, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee.
authors.forename: Yong C
authors.initials: YC
authors.lastname: Bradley
mesh_terms: D000818:Animals; D004621:Embolization, Therapeutic / Q000009:adverse effects*; D005260:Female; D011874:Radiometry; D011879:Radiotherapy Dosage; D013552:Swine; D041742:Upper Gastrointestinal Tract / Q000166:cytology* / Q000528:radiation effects*; D015021:Yttrium Radioisotopes / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D015021:Yttrium Radioisotopes
keywords: 90Y; SIRT; interventional oncology; radioembolization