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 patients with cancer undergoing FDG PET/CT. In this article, we present our institutional approach for management of COVID-19 vaccine-related lymphadenopathy on FDG PET/CT according to early experience. We suggest performing PET/CT at least 2 weeks after vaccination in patients with a cancer for which interpretation is anticipated to be potentially impacted by the vaccination but 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 postvaccination lymphadenopathy are provided, considering the lymph node's morphology and likely clinical relevance. Consideration should be given to administering the vaccine in the arm contralateral to a unilateral cancer to avoid confounding FDG uptake on the side of cancer. Our preliminary experience and suggested institutional approach should guide radiologists in management of patients with cancer undergoing PET/CT after COVID-19 vaccination.