The Effect of Oxygen Breathing and Radiotherapy upon the Tissue Oxygen Tension of some Human Tumours

1. Measurements of tissue oxygen tension have been made in human tumours which were being treated by high pressure oxygen radiotherapy. The measurements were made polarographically using a pulsed-voltage, membrane-covered electrode system. The electrodes measure mean oxygen tension over a circular area of 200 μ in diameter every 17 seconds. 2. While the patients were breathing air the mean oxygen tensions recorded in their tumours showed a very large scatter. In one patient's tumour which was studied the tension varied from 0 to 100 mm Hg. 3. Breathing 100 per cent oxygen at one atmosphere usually but not always produced an increase in oxygen tension. 4. Breathing 100 per cent oxygen at four atmospheres produced an increase in oxygen tension in all of the tumour sites which were studied. 5. Following irradiation there was an increase in tumour oxygen tension both while breathing air and 100 per cent oxygen at one atmosphere. The increase was, however, barely significant at the 5 per cent level. 6. The rate of saturation of the tumours with oxygen was often slower than in normal skin. There was no systematic change following radiotherapy. 7. Measurements of oxygen tension at one site in a tumour give no information concerning the oxygen tension at other sites. This emphasises the lack of homogeneity of the vascular pattern in tumours.