The medical use of gallium radionuclides: a brief history with some comments.

The use of gallium radionuclides in nuclear medicine dates back to the late 1940s, following the observation in toxicologic studies that gallium tended to localize to a high degree at sites of osteogenic activity. Initial attempts in the early 1950s to use 72Ga for clinical diagnosis and therapy of malignant bone lesions were unproductive. However, the basic information gained then in the preclinical and clinical investigations was quite instrumental in generating the present-day use of gallium radionuclides as effective radiopharmaceutical agents. Although initial clinical trials of 72Ga were unproductive, subsequent studies with 68Ga and 67Ga, together with advances in nuclear medical instrumentation, resulted in the identification of gallium radionuclides as effective tumor- and abscess-localizing agents. A major factor in the recognition of the peculiar biologic properties of gallium radionuclides was the existence of a carrier (stable isotope) effect. Also, it appears from basic studies of the mechanism(s) of the uptake of gallium in tumor tissue that the biodistribution of gallium involves many essential biologic processes. The future use of gallium radionuclides may, therefore, actually very well fall more into the field of basic biologic investigations rather than into the field of nuclear medical diagnosis.