COVID-19 Vaccination-Related Uptake on FDG PET/CT: An Emerging Dilemma and Suggestions for Management.

As mass COVID-19 vaccination is underway, radiologists are encountering transient FDG uptake in normal or enlarged axillary, supraclavicular, and cervical lymph nodes after ipsilateral deltoid vaccination. This phenomenon may confound interpretation in oncology patients undergoing FDG PET/CT. In this article, we present our institutional approach for management of COVID-19 vaccine-related lymphadenopathy on FDG PET/CT based on our early experience. We suggest performing PET/CT at least two weeks after vaccination in patients with a cancer for which interpretation is anticipated to be potentially impacted by the vaccination, though optimally 4-6 weeks after vaccination given increased immunogenicity of mRNA vaccines and potentially longer time for resolution than lymphadenopathy after other vaccines. PET/CT should not be delayed when clinically indicated to be performed sooner. Details regarding vaccination should be collected at the time of PET/CT to facilitate interpretation. Follow-up recommendations for post-vaccination lymphadenopathy are provided, considering the lymph node's morphology and likely clinical relevance. Consideration should also be given to administering the vaccine in the arm contralateral to a unilateral cancer to avoid potentially confounding FDG uptake on the side of cancer. Our preliminary experience and suggested institutional experience should guide radiologists in the management of oncology patients undergoing PET/CT after COVID-19 vaccination.