Prolonged generalized immune response on 18F-FDG PET/CT following COVID-19 vaccination

Abstract

The Coronavirus disease 2019 (COVID-19) pandemic continues to be a major public health concern affecting millions of people globally. The COVID-19 vaccination has implications in medical assessment of cancer patients especially undergoing diagnostic imaging such as ¹⁸F-fluoro-deoxyglucose (FDG) positron emission tomography with computed tomography (PET/CT). The inflammatory changes following vaccination can cause false positive findings on imaging. We present a case of a patient with esophageal carcinoma who had ¹⁸F-FDG PET/CT scan, 8 weeks following booster dose of Moderna COVID-19 vaccination, which showed widespread FDG avid reactive lymph nodes and intense splenic uptake for prolonged duration of approximately 8 months (34 weeks) probably representing generalized immune response. It is important from radiological/nuclear medicine perspective to recognize imaging features of such rare effect of COVID-19 vaccination, which can pose a challenge in assessing ¹⁸F-FDG PET/CT scans in cancer patients. It has also opened new avenues for future research evaluating such COVID-19 vaccine-related prolonged systemic immunological response in cancer patients.

Keywords: COVID-19; FDG; Immune response; Inflammation; PET/CT; Vaccination.

Fig. 1

The maximum intensity projection (MIP) image from initial ¹⁸F-fluoro-deoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) scan showed a hypermetabolic malignant mass in distal esophagus, liver metastases, and a hypermetabolic nodular lesion at the interface of stomach and transverse colon probably a malignant implant.

Fig. 2

The maximum intensity projection (MIP) image from follow-up ¹⁸F-fluoro-deoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) scan performed approximately 8 weeks following booster dose of Coronavirus disease 2019 (COVID-19) vaccine showed decreased or resolved fluoro-deoxyglucose (FDG) uptake in distal esophageal lesion, hepatic metastases and at gastric/colonic wall. However, there were new FDG avid cervical, thoracic, and abdominopelvic lymph nodes, diffuse splenic uptake without splenomegaly and focal moderate FDG uptake in the left deltoid muscle at the site of recent COVID-19 vaccine.

Fig. 3

The maximum intensity projection (MIP) image from follow-up ¹⁸F-fluoro-deoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) scan performed approximately 16 weeks after booster dose of Coronavirus disease 2019 (COVID-19) vaccine demonstrated persistently increased uptake in cervical, thoracic, and abdominopelvic lymph nodes, and diffuse splenic uptake.

Fig. 4

The maximum intensity projection (MIP) image from surveillance ¹⁸F-fluoro-deoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) scan performed approximately 23 weeks following booster dose of Coronavirus disease 2019 (COVID-19) vaccine, showed new hypermetabolic liver metastases, however decreased fluoro-deoxyglucose (FDG) uptake in cervical, thoracic, and abdominopelvic lymph nodes and spleen.

Fig. 5

The maximum intensity projection (MIP) image from subsequent ¹⁸F-fluoro-deoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) scan performed approximately 34 weeks following booster dose of Coronavirus disease 2019 (COVID-19) vaccine, showed decreased fluoro-deoxyglucose (FDG) avid hepatic metastases and resolved FDG activity in cervical, thoracic, and abdominopelvic lymph nodes and diffuse splenic uptake.