FDG-avid lymph nodes (LN) in response to vaccines for SARS-CoV-2

ABSTRACT

Aim/Introduction: Vaccines against SARS-CoV-2 virus were developed due to the impetuous coronavirus pandemic. Vaccines hold a possibility to provoke side effects. The aim of our study was to examine the impact of COVID-19 vaccination on the incidence and duration of false-positive FDG-avid lymphadenopathy after vaccination with different types of vaccines and to determine its relationship with age, gender, and vaccine type. Material(s) and Method(s) The retrospective study included 103 patients who met the following criteria18F-FDG PET/CT scan performed (in the period from August 2021 to December 2021) for staging or restaging of diagnosed oncological diseases at different time periods after vaccination Pfizer-BioNTech, Moderna-BioNTech and Oxford-AstraZeneca. Exclusion criteria were incomplete information about vaccination, patients with a diagnosed malignant lymphoproliferative disease, concomitant benign pathology of the lymphatic system, history of acute viral infection up to 3 months from the date of PET/CT. Result(s) False-positive reactive lymphadenopathy was identified in 35 (34%) of 103 patients included in our study cohort, which occurred during the first 2 weeks to 12 weeks after vaccination and manifested as increased metabolic activity in regional non-enlarged lymph nodes ipsilateral axillary lymph nodes of levels I-III, as well as cervical LN of levels IV and VB). A significant moderate decline in metabolic activity in the LN over time was reported, as well as a decrease in the detection rate of PET-positive reactive findings with time. The results showed a trend of a positive relationship - the occurrence of reactive lymphadenopathy more often in women than in men. The detection rate, as well as the intensity of the activity of glucose metabolism, were higher in patients under the age of 50 compared to those >= 50 years. However, we did not find significant differences between the studied types of vaccines (p >0.05). Conclusion(s) Multidisciplinary physician awareness is essential regarding the possibility of false-positive FDG lymphadenopathy in relation to local inflammation and as a manifestation of the immune response due to COVID-19 RNA vaccination and adenoviral vector-based vaccine up to 12 weeks after injection, in order to optimize the clinical interpretation of hybrid scan results that determine the subsequent therapeutic approach of cancer patients. The results of the present study demonstrate the importance of vaccination on the contralateral side of the tumor drainage, as well as taking a thorough anamnesis. Keywords FDG PET/CT, false positive lymphadenopathy, vaccination.