68Ga-Dotatate
Ga68 Dotatate Biodistribution.jpg
TRACER INFORMATION AND INDICATION
NETSPOT was approved by the FDA in 2016 for the detection and localization of somatostatin receptor-positive neuroendocrine tumors. This tracer is a somatostatin analog that binds to somatostatin receptors. Neuroendocrine neoplasms can occur anywhere in the body but are most common in the gastrointestinal tract, pancreas, and lungs. 68Ga is generator produced and has a 68 minute half-life.
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In 2020, 64Cu DOTA TATE (Detectnet) was approved for the same indications listed above. 64Cu can be either cyclotron or reactor produced and has a half-life of 12.7 hours.
CONTRAINDICATIONS
Long-acting somatostatin analogs will competitively bind to the somatostatin receptors. Therefore, imaging should occur prior to taking these. If patients have taken long-acting somatostatin analogs, a 28-day washout period is recommended before imaging. Short-acting somatostatin analogs can be used up to 24 hours before injection.
PATIENT PREPARATION
Patients should be well hydrated both before and after Pylarify injection to reduce radiation exposure.
RADIOPHARMACEUTICAL
In adults and pediatric patients, the recommended amount of 68Ga to be administered for PET imaging is 2 MBq/kg (0.054 mCi/kg) of body weight up to 200 MBq (5.4 mCi).
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In adults, the recommended amount of 64Cu to be administered for PET imaging is 148MBq (4mCi) and the injection should take place over one minute.
Imaging can begin 45 to 90 minutes after injection.
IMAGING PROTOCOL AND ACQUISITION PARAMETERS
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Instruct patient to void prior to imaging and change clothing if necessary.
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Imaging parameters are typically from the vertex to the mid-thigh with the patient having their arms raised above their head. Specific protocols including acquisition and uptake time should be checked with attending physicians as it may vary depending on scanner type.
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After imaging, instruct the patient to stay hydrated to reduce radiation exposure.
BIODISTRIBUTION
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Normal biodistribution includes kidneys, bladder, salivary glands, liver, spleen, and proximal small bowel. Low activity is also noted in the blood pool and muscle. Elimination is through the urine with 50% being eliminated within the first 8 hours after injection.
IMAGE INTERPRETATION
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Ga-68 dotatate binds to somatostatin receptors, so the intensity of the signals on the PET images indicate the presence and density of somatostatin receptors in tissues.
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Having knowledge of normal biodistribution is important for image interpretation. There are possibilities of false-positive interpretations for the following reasons:
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Accumulation of the tracer in the nasal and pulmonary hilar areas can be seen with respiratory infections.
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Diffuse pulmonary or pleural accumulation can potentially be observed after radiation therapy or bleomycin therapy.
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Accumulation can occur in recent surgical and colostomy sites.
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In addition, there are also potential causes for false positives for the following reasons:
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If the patient has unlabeled somatostatin, due to either octreotide therapy or because of possible somatostatin secretion of the tumor itself, there may be a decrease in tracer uptake.
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Liver metastasis may appear isointense because of a similar degree of uptake by the normal liver.
REIMBURSEMENT
Regarding the Radiopharmaceutical coding for NETSPOT, for dates of service January 1, 2017 and beyond, the HCPCS level II code and description is A9587 Gallium ga-68, dotatate, diagnostic, 0.1 millicurie (NDC #:69488-001-40). The Radiopharmaceutical coding for Detectnet, for dates of service April 1, 2021 and beyond, use the HCPCS code A9592 Copper Cu-64, dotatate, diagnostic, 1 millicurie (NDC #:69945-0064-01).
References
Detectnet (Cu-64 dotatate injection)[package insert]. Maryland Heights, MO. Curium US LLC. 2020.
Klimstra, David S. MD*; Modlin, Irvin R. MD, PhD†; Coppola, Domenico MD‡; Lloyd, Ricardo V. MD, PhD§; Suster, Saul MD∥ The Pathologic Classification of Neuroendocrine Tumors, Pancreas: August 2010 - Volume 39 - Issue 6 - p 707-712 doi: 10.1097/MPA.0b013e3181ec124e
Klöppel G: Neuroendocrine Neoplasms: Dichotomy, Origin and Classifications. Visc Med 2017;33:324-330. doi: 10.1159/000481390
NETSPOT (Ga-68 Dotatate Injection)[package insert]. Saint-Genis-Pouilly, France. Advanced Accelerator Applications USA, Inc. 2016.
NETSPOTTM (Ga-68 labeled DOTATATE, Injection) - SNMMI. (n.d.). https://www.snmmi.org/IssuesAdvocacy/QandADetail.aspx?ItemNumber=16038