Distribution of anticancer agents in spontaneous animal tumors. II. Distribution of gallium in canine lymphosarcoma.

The physiologic disposition of pharmacologic doses of gallium was studied in control dogs and dogs with spontaneous lymphosarcoma. Gallium 67 (67Ga) was administered iv with carrier gallium added at a dose of 8 mg/kg. About 50% of the injected dose was excreted in the urine by 48 hours (mostly in the first 12 hr), whereas negligible amounts were excreted in bile. The distribution of 67Ga in normal tissues was similar in control and tumor-bearing dogs. The tissue-to-plasma concentrations of gallium were considerably greater than 1 in the kidney cortex, bone marrow, bone, small intestine, and liver 6-72 hours after administration of the drug. At comparable time periods, tissue-to-plasma ratios of gallium were less than 1 in skeletal muscle and brain. In dogs with lymphosarcoma there was neither selective uptake nor selective retention of gallium in comparison to most normal tissues. In fact, several normal tissues, particularly kidney cortex and bone marrow, concentrated gallium greatly in excess of tumors. Qualitatively similar findings were obtained in a dog with malignant melanoma. These findings were contrary to what one would predict from reports showing that carrier-free 67Ga is selectively concentrated in various human and animal tumors. This indicates the need for more extensive studies of the physiologic disposition of pharmacologic (antitumor) doses of gallium in humans and appropriate animal models.