Measured Human Dosimetry of 68Ga-DOTATATE

Measured human dosimetry of the Ga-68-labeled synthetic somatostatin analog Ga-68-DOTATATE has not been reported in the peer-reviewed literature. Ga-68-DOTATATE is an investigational PET/CT imaging agent that binds with high affinity to somatostatin receptor subtype 2, found on many human cancers, most classically neuroendocrine tumors but also others. Reporting of measured dosimetry of Ga-68-DOTATATE could be useful for investigations for diagnosis, staging, and restaging of somatostatin receptor-expressing tumors. Methods: We performed measured dosimetry with Ga-68-DOTATATE PET/CT scanning in 6 volunteer human subjects as part of an Institutional Review Board-approved biodistribution investigation of the use of this radiopharmaceutical for possible future use in the diagnosis of indeterminate lung nodules or lung cancer. Five subjects were imaged at 3 time points, and 1 subject was imaged at 2 time points. Dosimetry was then measured for the whole body and for specific organs. Results: There were no observed adverse events to the radiopharmaceutical in the immediate or delayed time frames, with a follow-up of 1 y. One patient had stage IV non-small cell lung cancer and remains alive but with disease progressing on treatment. For the other 5 patients, it was ultimately proven that they had benign nodules. The measured dosimetry shows that the critical organ with Ga-68-DOTATATE is the spleen, followed by the uroepithelium of the bladder, the kidneys, and the liver, in that order. Organ-specific and whole-body dosimetries for Ga-68-DOTATATE were similar to but often slightly greater than those for Ga-68-DOTATOC or Ga-68-DOTANOC but less than those for In-111-diethylenetriaminepentaacetic acid-octreotide. Conclusion: No toxicity was observed in our 6 patients, and no adverse events occurred. The measured human dosimetry of Ga-68-DOTATATE is similar to that of other Ga-68-labeled somatostatin receptor analogs.