Direct Measurement of the PO2 Distribution in Human Malignant Brain Tumours

Malignant brain tumours are known to have a faster rate of recurrence and increased resistance to radiotherapy and chemotherapy than other solid tumours.1 One of the related causes is thought to be focal hypoxia,2 however the presence of hypoxic areas in malignant brain tumours has been disputed by PET studies and by the marginal effect of the hypoxic cell sensitisers such as Misonidazole.3 Low pO2 areas (<2.5mmHg) provide a source of radiobiological resistance,4 whereas pO2 levers less than 10–15 mmHg may provide conditions for the activation of new classes ofbioreductive agents.5 These agents require metabolic reduction under conditions of low oxygen tension to generate a cytotoxic species. In this study the oxygen status of peritumoural brain and tumour tissue has been measured to determine the presence of hypoxic regions and conditions for drug activation.