Clinical Workflow Differences in Ga-68 Dotatate vs Cu-64 Dotatate

Introduction: Ga-68 DOTATATE and Cu-64 DOTATATE are both positron emission tomography (PET) radiotracers used for imaging somatostatin receptor positive neuroendocrine tumors (NETs). The University of Tennessee Medical Center has been scanning with Ga-68 DOTATATE (NETSPOT) since 2017 and as of August 2021, the hospital switched to Cu-64 DOTATATE (Detectnet). These tracers will be referred to as Ga-68 and Cu-64 for the remainder of the abstract. The objective of this abstract is to compare the differences between Ga-68 and Cu-64 from a clinical workflow perspective.

Methods: Approximately 15 patients were observed that had both a Ga-68 and a Cu-64 scan. Each tracer was assessed to determine the differences in scheduling the exams, patient preparation, side effects, dose injection, and imaging guidelines. Image quality was not taken into consideration because our facility switched to a new PET/CT scanner when Cu-64 was introduced and image quality discussions have been sufficiently discussed in the literature.

Results: Scheduling

Before scheduling a Ga-68 or Cu-64 scan, verify the patient has been off long-acting somatostatin analogs for 28 days prior to imaging and short acting somatostatin analogs for 24 hours.

Patient Preparation

Patient preparation is the same for both tracers. Patients should be well hydrated and void frequently after the scan to reduce radiation dose to the kidneys and bladder. Patients must be off long-acting somatostatin analogs for 28 days prior to imaging and short acting somatostatin for 24 hours.

Side Effects

The only side effect observed when using Ga-68 was that several patients reported stinging at the injection site during injection. Some patients that were injected with Cu-64 began feeling nauseous within 5 minutes post injection. No other side effects were observed and all discomfort was transient.

Dose Injection Guidelines

Ga-68- 5.4mCi administered as intravenous bolus injection followed by saline flush

Cu-64- 4mCi administered as intravenous injection over 1 minute followed by saline flush

If necessary, volume can be adjusted by adding saline.

Imaging Guidelines

Both exams are scanned at 60 minutes post injection. Scan times are approximately 25 minutes for both Ga-68 and Cu-64. Cu-64 can be imaged between 45-90 minutes post injection.

Conclusions: The greatest difference in Ga-68 and Cu-64 from our facility is related to scheduling challenges. Ga-68 was more difficult to fit into the schedule because of the limitation in number of doses and specific calibration times. This is common with gallium tracers due to the limited output from gallium generators. However, Cu-64 was more difficult to cancel since it requires a 48-hour notice for cancellation, instead of 24 hours for Ga-68. The workflow after injection was not changed since both tracers were scanned at 60 minutes post injection. From a patient perspective, the length of the scan was the same and the only noticeable practice difference has been that we consistently observe patients feeling nauseous for approximately 5 minutes after the injection of Cu-64.