Hypermetabolic ipsilateral supraclavicular and axillary lymphadenopathy: Optimal time point for performing 18F-FDG PET/CT after COVID-19 vaccination

ABSTRACT

Ziel/Aim We aimed at evaluating the incidence of SARS-CoV2 vaccine-related axillary and supraclavicular hypermetabolic lymphadenopathy (HLA) and evaluate which timepoint produces the least number of false-positive findings in HLA. Methodik/Methods For this retrospective, multi-center imaging study patients with any form of SARS-CoV2 vaccination prior to 18F-FDG-PET/CT between January 2021 and December 2021 were included. Patients were divided into six groups according to the timepoint of vaccination prior to 18F-FDG-PET/CT imaging Group 1 (0-6 Days), Group 2 (7-13 Days), Group 3 (14-20 Days), Group 4 (21-27 Days), Group 5 (28-34 Days) and Group 6 (35-80 Days). As reference SUVmax of mediastinal blood pool (MBP) and SUVmax contralateral reference lymph node (RL) were determined. For each group, the following parameters were assessed. A) absolute SUVmax of HLA B) incidence of HLA [defined as the ratio of SUVmaxHLA/ SUVmax Mediastinal Blood Pool (rHLA/MBP)] greater than 1,5 C) rHLA/MBP D) ratio SUVmax HLA vs. SUVmax contralateral reference lymph node (rHLA/RL). Ergebnisse/Results HLA showed the highest incidence in Group 1(day 0-6) 16/23 (70 %). Similarly, SUVmax HLA and rHLA/MBP were highest in this group, SUVmax 4.97 +/- 4.1 and 2.58 +/- 2.1 respectively. The incidence of HLA, SUVmax HLA, and rHLA/MBP were higher in Group 3 (14-20 days) than in Group 2 (7- 13days);57 % vs 44 %;5.05 +/- 4.33vs 3.9 +/- 2.81 (p = 0.723 and 2.32 +/- 1.8 vs 1.83 +/- 1.38(p = 0.788). All parameters for HLA dropped markedly after at least 21 days of vaccination. There were no significant differences in SUVmax HLA, rHLA/MBP and rHLA/RL in group 4 (21-27 days), group 5 (28-34 days) and group 6 (35-80 Days). [1] Schlussfolgerungen/Conclusions It is crucial for diagnostic physicians to assess the recent history of COVID-19 vaccination prior to FDG-PET/CT scan to reduce the risk of false-positive calls. If feasible, FDG PET should be postponed by at least 3 weeks after SARS-CoV2 vaccination especially if an accurate evaluation of axillary status is required.