title: Fluctuations in pO2 in poorly and well-oxygenated spontaneous canine tumors before and during fractionated radiation therapy.
abstract: OBJECTIVE
  The spatial heterogeneity in oxygen tension (pO2) in tumor tissue has been studied extensively, whereas, the information about the temporal heterogeneity is sparse. The purpose of the present study was to search for pO2 fluctuations in untreated and irradiated spontaneous canine tumors, and to investigate whether there is a relationship between overall tumor oxygenation status and pO2 fluctuation pattern.
  
  
  METHODS
  Six dogs scheduled for radiation therapy of head and neck cancer were included in the study. The primary tumors were irradiated with 18 fractions of 3 Gy. Eppendorf polarographic electrodes and OxyLite fluorescence probes were used to measure overall oxygenation status and pO2 fluctuation pattern, respectively. Tissue pO2 was recorded at three subsequent days prior to treatment, and immediately before radiation fraction 4, 7, and 10.
  
  
  RESULTS
  Overall oxygenation status differed substantially among the tumors. Radiation therapy had no consistent effect on overall oxygenation status. Fluctuations in pO2 were detected in untreated as well as irradiated tumors, and independent of whether the tumors were poorly or well oxygenated.
  
  
  CONCLUSIONS
  Fluctuations in pO2 can occur in untreated and irradiated spontaneous canine tumors. There is no correlation between pO2 fluctuation pattern and overall tumor oxygenation status.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, Oslo, Norway.
authors.forename: Kjetil G
authors.initials: KG
authors.lastname: Brurberg
authors.forename: Hege K
authors.initials: HK
authors.lastname: Skogmo
authors.forename: Bjørn A
authors.initials: BA
authors.lastname: Graff
authors.forename: Dag R
authors.initials: DR
authors.lastname: Olsen
authors.forename: Einar K
authors.initials: EK
authors.lastname: Rofstad
mesh_terms: D000818:Animals; D015687:Cell Hypoxia / Q000528:radiation effects; D004195:Disease Models, Animal; D004285:Dogs; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D010101:Oxygen Consumption / Q000502:physiology*; D011878:Radiotherapy / Q000009:adverse effects* / Q000379:methods; D011879:Radiotherapy Dosage; D018570:Risk Assessment; D012680:Sensitivity and Specificity