Comparison of two techniques for detecting tumour hypoxia: a fluorescent immunochemical method and an in vitro colony assay.

The aim of this study was to compare the percentage of hypoxic cells obtained with two methods: an in vitro colony assay and a new method based on immunodetection of a marker for hypoxic cells (NITP) which could be used in patients. These studies have been carried out using one rodent tumour EMT6 (a mammary carcinoma) and one human tumour HRT18 (a rectal adenocarcinoma). The hypoxic cell fraction was assessed in control mice and in mice receiving two treatments: 250 mg/kg nicotinamide + carbogen, and 250 mg/kg nicotinamide + carbogen + 4 ml/kg perflubron emulsion. The two treatments increased the radiosensitivity of the two cell lines, nicotinamide plus carbogen plus perflubron emulsion having the greatest radiosensitising effect. For untreated and treated tumours, the percentage of hypoxic cells obtained with the in vitro colony assay were comparable to those obtained with immunodetection using NITP. Whatever the treatment, NITP detection was a convenient test to detect the hypoxic cell fraction in the two solid tumours we have studied.