Peri-tumoural hypoxia in human brain: peroperative measurement of the tissue oxygen tension around malignant brain tumours.

Malignant brain tumours contain focal hypoxic areas that may increase their resistance to chemotherapy and radiotherapy. Following surgical excision, the peri-tumoural area will contain residual viable tumour cells, and this area is therefore the logical site for subsequent therapy. The new bioreductive agents are metabolized under hypoxic conditions to produce a cytotoxic species. Peroperative peri-tumoural micro-polarographic measurements have been made to establish the oxygen environment of this region and to determine whether the hypoxic conditions might allow for bioreductive drug activation. The micro-polarographic method is described and results are presented for "normal" white matter (8 patients) to allow comparison with peri-tumoural brain (8 patients) before and after removal of the tumour. The results suggest that peri-tumoural brain (median pO2 10.8 mmHg, 18% pO2 < 2.5 mmHg) is markedly hypoxic in comparison with the "normal" brain (median pO2 15.3 mmHg, less than 2% < 2.5 mmHg), and that surgery improves peri-tumoural oxygenation towards that of the "normal" white matter. It is concluded that the hypoxic peri-tumoural area can provide the conditions under which bioreductive agents may be activated.