The Impact of different COVID-19 vaccines in 18F-FDG PET/CT

ABSTRACT

Aim/Introduction: Austria started its COVID-19-vaccination program in December 2020 with three different vaccines. As the vaccination program continues, we encountered increased F-18- FDG-activity not only in axillary lymph nodes ipsilateral to the injection site but also in other organs. The aim of this retrospective study is to present results of the metabolic activity of ipsilateral axillary lymph nodes, liver, blood pool, spleen, and bone marrow after three different vaccines. Material(s) and Method(s) The data of 220 eligible vaccinated patients (127 with BioNTech/Pfizer, 61 with Moderna, and 32 with AstraZeneca) examined with F18-FDG-PET/ CT were enrolled. The PET/CT examinations were evaluated from day 1 to day 120 (SD 23.2, Median 26) after different vaccinations. Seventy out of these 220 patients were at least once examined with F18-FDG-PET/CT before vacciantion. SUVmax of axillary node(s), and blood pool, liver, spleen, and bone marrow as reference organs were calculated. Relation of SUVmax activity of axillary lymph node to reference organs was also compared in all patients. Result(s) Ten days after BioNTech/Pfizer and AstraZeneca vaccination the axillary FDG uptake was at its highest activity. This was with Moderna vaccination after 30 days. There was no significant statistical difference of SUVmax of lymph nodes or its ratios to other reference organs between three groups of vaccines. SUVmax in lymph nodes in relation to SUVmax in the liver, spleen, and bone marrow was statistically significant with p-values of <.001, 0.044, and 0.001, respectively. In the group of 70 patients with a pre-vaccination PET/CT examination, the SUVmax of lymph nodes (median 0.820, standard deviation 1.233) changed significantly after vaccination (p <.001). A significant change of tracer activity in the liver was also observed (p = 0.032). There was no significant change of tracer activity after vaccination in other reference regions or between different types of vaccines. Conclusion(s) Local site and ipsilateral axillary lymph node activity in F18-FDG PET/CT after COVID19-vaccination is suggested in many studies. The main challenge is recognizing the changes in lymph nodes after vaccination to minimize false interpretation, foremost in patients with oncological diagnoses. Moreover, different vaccines cause different system metabolic changes. The knowledge of vaccine type, the time interval between vaccination and PET/CT scan is essential, especially in therapy evaluation.