Ultrasound guided, pre-radiation oxygen measurements using polarographic oxygen needle electrodes in spontaneous canine soft tissue sarcomas

Background: Poor tumour oxygenation is associated with radiation resistance. The recording of pre-treatment oxygenation status has been shown to be of prognostic relevance. Material and Methods: Eleven dogs with spontaneously arising soft tissue sarcomas were included in this study. Oxygen partial pressure measurements (pO(2)) were performed with the Eppendorf method. Results: The mean of median pO(2) was 9.6 mmHg (range: 0.1-30 mmHg). Four of the nine dogs included in the statistical analysis showed a median pO(2) less than or equal to 2.5mmHg. The natural logarithm of the hypoxic subvolume correlated with the hypoxic fraction less than or equal to 2.5 mmHg (p = 0.0712) and less than or equal to 5 mmHg (p = 0.0988). Mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV) correlated significantly to several oxygen parameters. Conclusion: Hypoxia exists in spontaneous canine soft tissue sarcomas and the dog can be used as a reliable model for repeated oxygenation measurements. Ultrasonography assures reliability of needle placement.