Incidental findings suggestive of COVID-19 pneumonia in oncological patients undergoing 18F-FDG PET/CT studies: association between metabolic and structural lung changes.

Although the novel coronavirus disease 2019 (COVID-19) can present as non-specific clinical forms, subclinical cases represent an important route of transmission and a significant source of mortality, mainly in high-risk subpopulations such as cancer patients. A deeper knowledge about the shift in cellular metabolism of Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected cells could provide new insights about its pathogenic and host response and help to diagnose pulmonary involvement. We explored the association between metabolic and structural changes of lung parenchyma in asymptomatic cancer patients with suspected COVID-19 pneumonia, as a potential added diagnostic value of fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) scans in this subpopulation. Methods: Within the period of February 19 and May 29, 2020 18F-FDG PET/CT studies were reviewed to identify those cancer patients with suggestive incidental findings of COVID-19 pneumonia. PET studies were interpreted through qualitative (visual) and semiquantitative analysis (measurement of maximum standardized uptake value, SUVmax) evaluating lung findings. Several characteristic signs of COVID-19 pneumonia on computed tomography (CT) were described as COVID-19 Reporting and Data System (CO-RADS) categories (1-6). After comparing SUVmax values of pulmonary infiltrates among different CO-RADS categories, we explored the best potential cut-off values of pulmonary SUVmax against CO-RADS categories as "gold standard" result to discard the diagnosis of COVID-19 pneumonia. Results: CT signs classified as CO-RADS category 5 or 6 were found in 16/41 (39%) oncological patients derived to multimodal PET/CT imaging. SUVmax was higher in patients with CO-RADS 5 and 6 vs. 4 (6.17±0.82 vs. 3.78±0.50, P = 0.04) and vs. 2 and 3 categories (3.59±0.41, P = 0.01). A specificity of 93.8% (IC 95%: 71.7-99.7%) and an accuracy of 92.9% were obtained when combining a CO-RADS score 5-6 with a SUVmax of 2.45 in pulmonary infiltrates. Conclusion: In asymptomatic cancer patients, the metabolic activity in lung infiltrates is closely associated with several combined tomographic changes characteristic of COVID-19 pneumonia. Multimodal 18F-FDG PET/CT imaging could provide additional information during early diagnosis in selected predisposed patients during pandemic. The prognostic implications of simultaneous radiological and molecular findings in cancer and other high-risk subpopulations for COVID-19 pneumonia deserve further evaluation in prospective researches.