Relative tumour enhancement of67Ga uptake by desferrioxamine

The administration of the iron- and gallium-chelating agent, desferrioxamine (DFO), to mice after the injection of⁶⁷Ga has been shown to improve tumour to normal tissue ratios. Time and dose parameters have been studied. The optimal time was about 7 h after⁶⁷Ga, when the tumour to blood ratio was increased 16 times compared with controls. The effect was due to the greater retention of⁶⁷Ga in tumour compared with other tissue. Tumour retention after DFO was 78% compared with controls at 7 h, giving a tumour to blood ratio of 25.9. Tumour retention of⁶⁷Ga correlated well with the proportion of cell-bound activity which was localised in the lysosomes.Prior administration of iron increased lysosomal accumulation of⁶⁷Ga in tumour cells, and hence the retention of the nuclide after the use of DFO.