Tumor imaging with novel radiogallium ([sup 67/68]Ga) labeled agents

Abstract

Gallium-67 (t1/2: 78 h) has played an important role in tumor imaging. It is produced in a cyclotron and is commercially available for routine clinical use. 68Ga (t1/2: 68 min), a positron emitter, suitable for positron emission tomographic (PET) imaging, is obtained from a generator with long lived parent 68Ge (t1/2: 288 d). Radiogallium has been used mostly, as gallium citrate in imaging studies. Recently, receptor specific agents labeled with gallium have been developed. These include, agents to image somatostatin and folate receptors. We have shown that a new class of agents based on glycosaminoglycoans (GLYCOS) target a variety of tumors. Gallium labeled deferroxamine (DF) bound to sulfated glycosaminoglycans has the ability to rapidly target and permeate a wide variety of solid animal tumors and also undergo rapid blood clearance almost exclusively by the renal route. We have been able to image (within 5 min to 1 hr), prostate adenocarcinoma (AT-1 tumor) grown in surgically prepared pedicles of Copenhagen male rats and breast tumor in pedicles of Fisher female rats. 67Ga labeled agent was used in single photon imaging mode and 68Ga labeled agent was used in PET mode with a small animal PET imaging device built in our laboratory with plastic scintillating optical fibers.