Effect of Carrier on the Distribution of ⁵⁴Mn and ⁶⁷Ga in Tumor-Bearing Animals

Abstract

The simultaneous administration of carrier gallium has been shown [1] to change the biodistribution of carrier-free ⁶⁷Ga from one of predominately soft-tissue distribution to localization primarily in bone and kidney. In tumor-bearing animals, administration of carrier gallium significantly reduced ⁶⁷Ga accumulation in tumor tissue [2]. There is little available data concerning the effect of carrier on the tissue distribution and tumor localization of ⁶⁷Ga. when the interval between the injection of carrier and tracer is varied. Conceivably, carrier material appropriately administered might offer a useful means of affecting tracer distribution in a tumor-bearing host and enhance the lesion-background ratios of tumor-seeking radiopharmaceuticals. We explored this question for both Ga/⁶⁷Ga (a trace metal with no known intracellular function) [3] and Mn/⁵⁴Mn, and ion known to enter mitrochondia [4] and intimately associated with cellular metabolism [5]. Since both of these metals develop high tumor-background ratios [3,6], have positron-emitting isotopes suitable for use with the newer positron-imaging devices, and have been shown to alter tumor growth rates [7–9], these data might be useful for both diagnosis and therapy.