Discussion:
68Ga-labeled somatostatin receptor PET/CT pitfalls:
Some pitfalls during 68Ga-labeled somatostatin receptor (such as DOTATATE, DOTATOC, DOTANOC) PET/CT have been reported as causes of misdiagnoses such as:
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Iatrogenic Microembolism
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Inflammatory/ Infectious process
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Non-ossifying fibroma
Iatrogenic microembolism as a cause of 18F-FDG embolus is well-established; however, 68Ga-DOTATOC embolus is not well-documented in the literature[1].
Al-Ibraheem A, Sweedat DA, Anwer F, Istatieh F, Juweid ME. 68Ga-DOTATOC Embolus Manifestation and Spontaneous Resolution by PET/CT. Nucl Med Mol Imaging. 2022 Aug;56(4):208-210. doi: 10.1007/s13139-022-00752-8. Epub 2022 May 12. PMID: 35846418; PMCID: PMC9276866.
This case [1] was a 64 male patient with a history of a well-differentiated gastric NET 5 years ago. Underwent partial gastrectomy and has been on Sandostatin for the last 4 years. This was a follow-up 68Ga-DOTATOC study which showed remission with no metastasis.
However, a focal uptake was seen in the medial aspect of the RUL, appreciated only on the PET with no corresponding CT finding.
The patient was symptom-free. This finding was assumed as a pitfall, mostly caused by radioactive embolus secondary to tracer clumping.
It was confirmed by a 68Ga-DOTATOC PET/CT performed 6 months later showing resolution of lung uptake and any morphologic findings on the CT, without any intervening treatment [1}.
The second differential diagnosis is an inflammatory process. Increased DOTATATE activity can be seen in the inflammatory process due to the overexpression of somatostatin receptors on macrophages which accumulated at the site of the infectious/ inflammatory process.
We can differentiate these two diagnoses with attention to the patient history, physical examination, and follow-up imaging.
68Ga DOTA-TOC PET/CT . Khalaf, A., Hirmas, N., Anwer, F. et al. 68Ga DOTA-TOC Uptake in Non-ossifying Fibroma: a Case Report. Nucl Med Mol Imaging 54, 199–203 (2020). https://doi-org.proxy.bib.uottawa.ca/10.1007/s13139-020-00650-x
In a case report from Khalaf, A. et al, [2] in the MIP image there is a focal somatostatin receptor-positive lesion ( SUVmax = 2.52) was identified, within the distal left femur (a) corresponding well-defined lytic bone lesion, indicative of non-ossifying fibroma.
References:
1. Al-Ibraheem A, Sweedat DA, Anwer F, Istatieh F, Juweid ME. 68Ga-DOTATOC Embolus Manifestation and Spontaneous Resolution by PET/CT. Nucl Med Mol Imaging. 2022 Aug;56(4):208-210. doi: 10.1007/s13139-022-00752-8. Epub 2022 May 12. PMID: 35846418; PMCID: PMC9276866.
2. Khalaf, A., Hirmas, N., Anwer, F. et al. 68Ga DOTA-TOC Uptake in Non-ossifying Fibroma: a Case Report. Nucl Med Mol Imaging 54, 199–203 (2020). https://doi-org.proxy.bib.uottawa.ca/10.1007/s13139-020-00650-x