Assessment of extra-parenchymal lung involvement in asymptomatic cancer patients with COVID-19 pneumonia detected on 18F-FDG PET-CT studies

Abstract

Background Lung involvement in patients with coronavirus disease 2019 (COVID-19) undergoing PET-CT has been previously reported. However, FDG uptake outside lung parenchyma was poorly characterized in detail. We evaluated the extraparenchymal lung involvement in asymptomatic cancer patients with COVID-19 pneumonia through 18 F-FDG PET-CT. Methods A total of 1079 oncologic 18 F-FDG PET-CT were performed between February 2 and May 18, 2020. Confirmed COVID-19 pneumonia was defined as characteristic ground-glass bilateral CT infiltrates and positive genetic/serologic tests. Nonmetastatic extra-parenchymal lung PET-CT findings were evaluated through qualitative (visual), quantitative (measurements on CT), and semiquantitative (maximum standardized uptake value: SUVmax on PET) interpretation. Clinical data, blood tests, and PET-CT results were compared between patients with and without COVID-19 pneumonia. Results A total of 23 18 F-FDG PET-CT scans with pulmonary infiltrates suggestive of COVID-19 and available laboratory data were included: 14 positive (cases) and 9 negative (controls) for COVID-19 infection, representing a low prevalence of COVID-19 pneumonia (1.3%). Serum lactate dehydrogenase and D-dimers tended to be increased in COVID-19 cases. Extraparenchymal lung findings were found in 42.9% of patients with COVID-19, most frequently as mediastinal and hilar nodes with 18 F-FDG uptake (35.7%), followed by incidental pulmonary embolism in two patients (14.3%). In the control group, extrapulmonary findings were observed in a single patient (11.1%) with 18 F-FDG uptake located to mediastinal, hilar, and cervical nodes. Nasopharyngeal and hepatic SUVmax were similar in both groups. Conclusion In cancer patients with asymptomatic COVID-19 pneumonia, 18 F-FDG PET-CT findings are more frequently limited to thoracic structures, suggesting that an early and silent distant involvement is very rare. Pulmonary embolism is a frequent and potentially severe finding raising special concern. PET-CT can provide new pathogenic insights about this novel disease.

Role of 2-[18F]FDG as a Radiopharmaceutical for PET/CT in Patients with COVID-19: A Systematic Review

“…One study found that 2-[ 18 F]FDG uptake of pulmonary CT abnormalities, in particular in cases of consolidation areas, were significantly lower in patients with a final diagnosis of COVID-19 compared to those who were negative for COVID-19 [8]. Conversely, another study did not find a significant difference of 2-[ 18 F]FDG uptake in ground glass pulmonary infiltrates between COVID-19 patients and controls [17]. Some studies reported that the prevalence of incidental pulmonary findings suspicious for interstitial pneumonia by COVID-19 at 2-[ 18 F]FDG PET/CT was higher when compared to 2-[ 18 F]FDG PET/CT scans of the same period one year earlier, without significant differences in 2-[ 18 F]FDG uptake [7,12,13,16].…”

“…From the comprehensive computer literature search of PubMed/MEDLINE and Cochrane databases, 169 records were screened. In total, 11 studies were selected and retrieved in full-text version according to the predefined inclusion criteria [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Conversely, 158 records were excluded because case reports or small case series ( n = 51), reviews, editorials, letters ( n = 39) or because they were outside the field of interest of this review ( n = 68).…”

“…In most of the studies, 2-[ 18 F]FDG PET/CT was performed in patients evaluated for standard indications (mostly oncological indications) and incidental findings suspicious of SARS-CoV-2 infection or COVID-19 at whole-body 2-[ 18 F]FDG PET/CT were described [ 7 , 8 , 9 , 10 , 12 , 13 , 14 , 15 , 16 , 17 ]. Only in one study 2-[ 18 F]FDG PET/CT was performed in COVID-19 patients to assess the inflammatory status at the presumed peak of the inflammatory phase [ 11 ].…”

“…Most of the included studies reported the rate of incidental findings suspicious of SARS-CoV-2 infection or COVID-19 at 2-[ 18 F]FDG PET/CT performed for standard indications. This rate largely varied among the included studies from 2.1% to 16.2% of all whole body 2-[ 18 F]FDG PET/CT scans [ 7 , 8 , 9 , 12 , 13 , 14 , 15 , 16 , 17 ], based on the prevalence of SARS-CoV-2 infection or COVID-19 during the examination period in a specific country or region [ 11 , 12 , 16 ]. A significant association of the appearance of imaging findings suspicious for COVID-19 on 2-[ 18 F]FDG PET/CT with gender, sex, age, or ethnicity was not demonstrated [ 12 ].…”

“…A significant association of the appearance of imaging findings suspicious for COVID-19 on 2-[ 18 F]FDG PET/CT with gender, sex, age, or ethnicity was not demonstrated [ 12 ]. Only a percentage of suspicious COVID-19 at 2-[ 18 F]FDG PET/CT was finally confirmed by further examinations (e.g., RT-PCR or serological testing) [ 7 , 8 , 9 , 10 , 12 , 13 , 14 , 15 , 16 , 17 ].…”