Retrospective Study Of ¹⁸F-FDG PET/CT Imaging In Differential Diagnosis Of Pulmonary Fungal Infections And Lung Cancer

Background:Pulmonary fungal infections,especially for those characterized by solitary pulmonary nodules or masses,are difficult to distinguish them from lung cancer.¹⁸F-FDG PET/CT has been widely used to the differential diagnosis of solitary pulmonary nodule or mass,little is known about the ¹⁸F-FDG PET/CT findings of pulmonary fungal infections.We aimed to summarize the ¹⁸F-FDG PET/CT findings of pulmonary fungal infection,and evaluate its diagnostic value in differential diagnosis between pulmonary infections and lung cancer.Methods:The clinical and ¹⁸F-FDG PET/CT imaging data of 21 patients with pulmonary fungal infection（n=21）and 42 patients with lung cancer（n=42）in the First Affiliated Hospital of Guangxi Medical University from January2008 to December 2017 were retrospectively analyzed and compared.The group of lung cancer was selected by total random sampling among patients who confirmed lung cancer and evaluated by ¹⁸F-FDG PET/CT.Only Confirmed pulmonary fungal infection cases were included.Results:1.Among the 21 patients with pulmonary fungal infection,10 were male,With a mean age of（55.57±16.55）years.As to 42 patients with lung cancer,30 were male with a mean age of（57.40±9.64）years.There was no statistical difference between the two groups.There are 2 cases of patients with pulmonary fungal infection combined with diabetes or long-term glucocorticoid treatment,and 1case of HIV infection.There was also no statistical difference between the two groups.52.38%pulmonary fungal infection cases were misdiagnosed by lung cancer.2.Among patients with pulmonary fungal infection,fever is more common,and statistical difference was found between the two groups（p=0.000）.No statistical difference was found in symptoms like cough or emptysis between the two groups.3.The median value of white blood cell count of the pulmonary fungal infection group was 12.20×10⁹/L,higher than that of the lung cancer group with the median value of 7.91×10⁹/L（p=0.030）.Significant difference was found in the neutrophil counts.There was no significant difference in the lymphocyte counts,serum high-sensitivity C-reactive protein,erythrocyte sedimentation rate,CD⁴+cells,CD⁸+cells and immunoglobulin between the two groups.4.There was no statistical difference between the CT imaging features such as spiculated border or pleural indentation etc.Statistically significant was not found in the size of pulmonary nodules or mass.The involvement of bilateral pulmonary were more common in the group of pulmonary fungal infection（p=0.002）.Lung cancers,as well as pulmonary fungal infection,cause the lesions of bone and lymph node,and as to the lesions of lymph node there was statistical difference between them.5.For patients with pulmonary fungal infection,standardized uptake value max（SUVmax）was 1.5-17.3（median7.90,n=17）;13 patients’SUVmax were higher than 2.5（median SUVmax9.90）.For patients with lung cancer,SUVmax1.6-34.5（median 8.80）.SUVmax was not significantly different between two groups.There were 4 patients with pulmonary fungal infection demonstrated no¹⁸F-FDG uptake,and statistically significant was found between two groups（p=0.018）.6.The pathogen results of pulmonary fungal infection were analyzed in three different groups.The SUVmax in the cryptococcal infection group was 1.2-17.3（median5.1,n=7）,Aspergillus infection group 1.5-16.5（median9.85,n=3）,Penicillium marneffei group 3.3-14.4（median8.2,n=7）.SUVmax was no significantly different among these three groups.Conclusion:1.For pulmonary fungal infections which characterized by solitary pulmonary nodules or masses,the ¹⁸F-FDG PET/CT findings such as CT imaging features or SUVmax are no significant difference between patients with pulmonary fungal infection and patients with lung cancer.Thus it’s difficult to identify these two diseases.2.41 histology proved lung cancer patients shows increased ¹⁸F-FDG uptake,usually the diagnosis of pulmonary fungal infection could be made in condition of that shows no ¹⁸F-FDG uptake.However it’s difficult to make a diagnosis when SUVmax is less than 2.5.There no significantly different was found in SUVmax.3.For patients with pulmonary fungal infection,characterized by solitary pulmonary nodules or masses and increased ¹⁸F-FDG uptake,which usually lead to the misdiagnosis of lung cancer and surgical treatment.Thus Pathogen detection should be undertaken among patients with positive PET results and those with positive mycological test results.The uptake of ¹⁸F-FDG was no significantly different among patients with cryptococcal infection、aspergillus infection and penicillium marneffei.