title: Oxygenation of spontaneous canine tumors during fractionated radiation therapy.
abstract: OBJECTIVE
  Tumor oxygenation predicts treatment outcome, and reoxygenation is considered important in the efficacy of fractionated radiation therapy. Therefore, the purpose of this study was to document the changes of the oxygenation status in spontaneous canine tumors during fractionated radiation therapy using polarographic needle electrodes.
  
  
  METHODS
  Tumor oxygen partial pressure (pO(2)) measurements were performed with the Eppendorf-pO(2)-Histograph. The measurements were done under general anesthesia, and probe tracks were guided with ultrasound. pO(2) was measured before radiation therapy in all dogs. In patients treated with curative intent, measurements were done sequentially up to eight times (total dose: 45-59.5 Gy). Oxygenation status of the palliative patient group was examined before each fraction of radiation therapy up to five times (total dose: 24-30 Gy).
  
  
  RESULTS
  15/26 tumors had a pretreatment median pO(2) < or = 10 mmHg. The pO(2) values appeared to be quite variable in individual tumors during fractionated radiation therapy. The pO(2) of initially hypoxic tumors (pretreatment median pO(2) < or = 10 mmHg) remained unchanged during fractionated radiotherapy, whereas in initially normoxic tumors the pO(2) decreased.
  
  
  CONCLUSIONS
  Hypoxia is common in spontaneous canine tumors, as 57.7% of the recorded values were < or = 10 mmHg. The data of this study showed that initially hypoxic tumors remained hypoxic, whereas normoxic tumors became more hypoxic.
authors.affiliation: Section of Diagnostic Imaging and Radiation Oncology, Veterinary School, University of Zurich, Switzerland.
authors.forename: Roger E
authors.initials: RE
authors.lastname: Achermann
authors.forename: Stefanie M
authors.initials: SM
authors.lastname: Ohlerth
authors.forename: Carla
authors.initials: C
authors.lastname: Rohrer Bley
authors.forename: Max
authors.initials: M
authors.lastname: Gassmann
authors.forename: Natalie
authors.initials: N
authors.lastname: Inteeworn
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Roos
authors.forename: Myriam
authors.initials: M
authors.lastname: Schärz
authors.forename: Melanie C
authors.initials: MC
authors.lastname: Wergin
authors.forename: Barbara
authors.initials: B
authors.lastname: Kaser-Hotz
mesh_terms: D000818:Animals; D015687:Cell Hypoxia / Q000528:radiation effects; D004283:Dog Diseases / Q000378:metabolism* / Q000532:radiotherapy*; D004285:Dogs; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D005260:Female; D008297:Male; D009369:Neoplasms / Q000378:metabolism / Q000532:radiotherapy / Q000662:veterinary*; D010100:Oxygen / Q000378:metabolism*; D011048:Polarography / Q000662:veterinary; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
chemical_list: D010100:Oxygen