title: Microbrachytherapy using holmium-166 acetylacetonate microspheres: a pilot study in a spontaneous cancer animal model.
abstract: OBJECTIVE
  Holmium-166 acetylacetonate microspheres ((166)Ho-AcAc-MS) are proposed as an intratumoral radioablation device. This article presents a pilot study in housecats with unresectable liver cancer. Feasibility and tolerability of intratumoral administrations of (166)Ho-AcAc-MS was investigated.
  
  
  METHODS
  Three cats with unresectable liver tumors of different histotype were included. One cat had hepatocellular carcinoma (HCC), one had cholangiocarcinoma (CC), and one had a malignant epithelial liver tumor (MELT) of unspecified histotype. (166)Ho-AcAc-MS were injected percutaneously under ultrasound guidance into the tumors. Followup consisted of physical examinations and hematologic and biochemical analyses.
  
  
  RESULTS
  (166)Ho-AcAc-MS were administered to three liver tumor-bearing cats. The treatment was well tolerated and the clinical condition, that is body weight, alertness, mobility, and coat condition of the animals improved markedly. Most biochemical and hematologic parameters normalized shortly after treatment. Life of all cats was extended and associated with a good quality of life. The HCC cat that received 33-Gy tumor-absorbed dose was euthanized 6 months after the first administration owing to disease progression. The MELT cat received 99-Gy tumor dose and was euthanized 3 months posttreatment owing to bacterial meningitis. The CC cat received 333Gy and succumbed 4 months after the first treatment owing to the formation of a pulmonary embolism.
  
  
  CONCLUSIONS
  Percutaneous intratumoral injection of radioactive (166)Ho-AcAc-MS is feasible in liver tumor-bearing cats. The findings of this pilot study indicate that (166)Ho-AcAc-MS may constitute safe brachytherapeutic microspheres and warrant studies to confirm the clinical utility of this novel brachytherapy device.
authors.affiliation: Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Wouter
authors.initials: W
authors.lastname: Bult
authors.forename: Maarten A D
authors.initials: MA
authors.lastname: Vente
authors.forename: Eva
authors.initials: E
authors.lastname: Vandermeulen
authors.forename: Ingrid
authors.initials: I
authors.lastname: Gielen
authors.forename: Peter R
authors.initials: PR
authors.lastname: Seevinck
authors.forename: Jimmy
authors.initials: J
authors.lastname: Saunders
authors.forename: Alfred D
authors.initials: AD
authors.lastname: van Het Schip
authors.forename: Chris J G
authors.initials: CJ
authors.lastname: Bakker
authors.forename: Gerard C
authors.initials: GC
authors.lastname: Krijger
authors.forename: Kathelijne
authors.initials: K
authors.lastname: Peremans
authors.forename: Johannes F W
authors.initials: JF
authors.lastname: Nijsen
mesh_terms: D000818:Animals; D001918:Brachytherapy / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D002415:Cats; D045744:Cell Line, Tumor; D006695:Holmium / Q000009:adverse effects / Q000737:chemistry / Q000627:therapeutic use*; D006885:Hydroxybutyrates / Q000737:chemistry*; D008113:Liver Neoplasms / Q000532:radiotherapy*; D008863:Microspheres; D008904:Miniaturization; D010422:Pentanones / Q000737:chemistry*; D010865:Pilot Projects; D011868:Radioisotopes / Q000009:adverse effects / Q000737:chemistry / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D006885:Hydroxybutyrates; D010422:Pentanones; D011868:Radioisotopes; C049529:acetyl acetonate; D006695:Holmium