COVID vaccination may confound cancer detection through PET imaging: Study
Rochester, MN: PET imaging performed after COVID-19 vaccination showed abnormal radiotracer uptake in the lymph nodes of cancer patients, according to a recent study. There had been no visible axillary node uptake prior to the vaccinations.
The findings, published in the American Journal of Roentgenology, indicate that these alterations in PET findings after the COVID-19 vaccination are important confounding pitfalls that could prompt unnecessary biopsies and treatments unless appropriately recognized by interpreting physicians.
Confounding imaging interpretation, COVID-19 vaccination may trigger reactive lymphadenopathy. However, there has been limited systematic analysis of PET findings after the COVID-19 vaccination. To fill this knowledge gap, Dane G. Schroeder, Mayo Clinic Department of Radiology, Rochester, Minnesota, and colleagues aimed to evaluate the frequency and characteristics of abnormal FDG and 11C-choline uptake on PET imaging performed after COVID-19 vaccination.
For this purpose, the researchers performed a retrospective study of 67 patients who underwent PET examination (PET/CT in 66, PET/MRI in 1; FDG in 54, 11C-choline in 13) between December 14th, 2020 and March 10th, 2021 following COVID-19 vaccination (Pfizer-BioNTech vaccine in 52, Moderna vaccine in 15) and who had undergone pre-vaccination PET without visible axillary node uptake. In patients who had received one (n = 44) and two (n = 23) doses, PET was performed after a median of 13 and 10 days after vaccination.
Key findings of the study include:
- Positive axillary lymph node uptake was observed in 10.4% of patients [7.4% of FDG examinations, 23.1% of 11C-choline examinations]; four and three patients with positive axillary lymph nodes had received Pfizer and Moderna vaccines, respectively.
- Injection laterality was documented in five of seven patients with positive axillary lymph nodes and was ipsilateral to the positive node in all five patients.
- PET was performed within 24 days of vaccination in all patients with a positive node.
- One patient exhibited extra-axillary lymph node uptake (ipsilateral supraclavicular uptake on FDG PET).
- Ipsilateral deltoid uptake was present in 14.5% (8/55) of patients with documented injection laterality, including in 42.9% (3/7) of patients with positive axillary lymph nodes.
- Interreader agreement for SUV measurements ranged from intraclass correlation coefficient of 0.600 to 0.988.
"Our findings demonstrate that increased axillary lymph node or ipsilateral deltoid uptake is occasionally observed on FDG or 11C-choline PET performed after Pfizer-BioNTech or Moderna COVID-19 vaccination," wrote the authors.
"Interpreting physicians should recognize characteristics of abnormal uptake on PET after COVID-19 vaccination to guide optimal follow-up management and reduce unnecessary biopsies," they concluded.
Reference:
The study titled, "Frequency and Characteristics of Nodal and Deltoid FDG and 11C-Choline Uptake on PET Imaging Performed After COVID-19 Vaccination," is published in the American Journal of Roentgenology.
DOI: https://www.ajronline.org/doi/10.2214/AJR.21.25928
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