The British journal of surgery
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A lung colony assay for clonogenic cells of human tumours in immune-suppressed mice is presented. The assay was used to determine the chemosensitivity of two malignant melanomas. One tumour reproduced the spectrum of chemosensitivity associated clinically with three cytotoxic agents. ⋯ An invesitgation of the importance of size as a determinant of response to radiotherapy demonstrated that 0.5-mm diameter tumour nodules were significantly more sensitive to irradiation than 2-cm diameter nodules. The hypoxic fraction of the larger tumours was 65 per cent, which is higher than that reported for experimental animal tumours or a human pancreatic tumour. This could be a factor in the clinical radioresistance of malignant melanoma.