ABSTRACT
Aim/Introduction: During the COVID 19 pandemic, mass vaccination campaign has played an important role, with a special importance in oncological and immunosuppressed patients, who form a large part of our [18F]FDG-PET/CT studies. Unexpected findings in the form of reactive lymphadenopathy were commonly detected in [18F]FDG-PET/CT studies. It is essential to recognize them and adapt their interpretation to the current epidemiological context. Material(s) and Method(s): Retrospective study of consecutive [18F] FDG-PET/CT studies performed at our center in 219 patients with oncological pathology from June 15 to September 20, 2021. A structured interview was conducted on all the patients who came to undergo [18F]FDG-PET/CT, in which they were asked about the type, date and arm of administration of the vaccine. The frequency of appearance of reactive lymphadenopathy, its relationship with the type of vaccine, sex, age and the importance of a detailed clinical interview prior to the isotope injection and/ or study interpretation were analyzed. Patients that presented ipsilateral axillary lymphadenopathies following vaccination and presented increased metabolic activity regardless of node size were considered positive, size and SUVmax were assessed. Result(s): From De 219 patients reviewed, 32% presented positive [18F]FDG-PET/CT axillary lymph nodes ipsilateral to the arm where the vaccine was inoculated. There was a relationship (p=0.01) between the mean size of the lymph nodes (11+/-9mm) and its mean metabolic activity (3.7+/-2.6 SUVmax). The appearance of lymphadenopathy was more frequent in women (40.5% vs 21% p<0.001), in younger patients (mean age 53+/-14 years vs 68.5+/-13 years p<0.001), in patients who had received the Moderna vaccine (58.5% p<0.001) and in which the time elapsed between vaccination and the performance of [18F]FDG-PET/CT was shorter. Conclusion(s): The appearance of post SARS-CoV2-vaccination reactive lymphadenopathies has been a frequent finding in [18F]FDG-PET/CT despite the main oncological indication of the study. Knowing the circumstances of these findings in oncological patients is important when interpreting them, so the use of a structured directed clinical interview has been very useful to help the physician understand and differentiate these findings.