An interpretation of the results of measurements of the uptake of32P in human tumours

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Abstract
Continuous uptake measurements have been made following a single oral administration of 32P-orthophosphate, using Geiger counters implanted in normal and malignant human tissues and the resulting recordings have been analysed statistically using a computer. After the initial equilibration period the experimental data are described satisfactorily by a single exponential function whose parameters may be modified by hormone administration. Fluctuations in radioactivity occur whose variance is significantly greater for tumours than for normal resting tissue. The data have been examined for possible periodicities; both normal and malignant tissue exhibit increased variance at low frequencies but in only one out of 14 cases (breast tumours) is a regular cycle apparent, the rhythm being circadian. The two most likely causes of the observed fluctuations in radioactivity are changes in blood flow or variations in metabolic activity within the tissue volume being measured. When the blood only was labelled with DF32P the fluctuations in radioactivity were found to have a smaller variance than was observed in the same tissues after subsequent administration of 32P-orthophosphate. Biochemical analysis of tumour biopsy samples showed that the specific activity of the acid-soluble phosphorus and the RNA phosphorus was always greater at a “peak” in the radioactivity records than at the subsequent “trough”. These data suggest that the observed fluctuations in radioactivity are largely metabolic in origin.