Whole body ¹⁸F-FDG PET/CT is superior to CT as first line diagnostic imaging in patients referred with serious non-specific symptoms or signs of cancer: a randomized prospective study of 200 patients

Abstract

A fast-track pathway has been established in Denmark to investigate patients with serious non-specific symptoms and signs of cancer (NSSC), which are not eligible to enter an organ-specific cancer program. The prevalence of cancer in this cohort is approximately 20%. The optimal screening strategy in patients with NSSC remains unknown. The aim was to investigate if ¹⁸F-FDG-positron emission tomography/computed tomography (PET/CT) was superior to CT as initial imaging modality in patients with NSSC. In a randomized prospective trial the imaging modalities were compared with regard to diagnostic performance. METHODS: A total of 200 patients were randomized 1:1 to whole body ¹⁸F-FDG-PET/CT or CT of the thorax and abdomen as imaging modality. A tentative diagnosis was established after first line imaging. The final referral diagnosis was adjudicated by the physician, when sufficient data was available. RESULTS: A total of 197 patients were available for analysis as 3 patients withdrew consent prior to scan. Thirty-nine (20%) were diagnosed with cancer, 10 (5%) with an infection, 15 (8%) with an autoimmune disease and 76 (39%) with other diseases. In 57 patients (28%) no specific disease was found. Compared to CT scans, ¹⁸F-FDG-PET/CT had a higher specificity (96 vs. 85%; P = 0.028) and a higher accuracy (94 vs. 82%; P = 0.017). However, there were no statistically significant differences in sensitivity (83 vs. 70%) or negative predictive values (96 vs. 92%). No difference in days to final referral diagnosis according to randomization group could be shown (7.2 vs. 7.6 days). However, for the subgroups where the imaging modality showed suspicion of malignancy, there was a significant delay to final diagnosis in the CT group compared to the ¹⁸F-FDG-PET/CT group (11.6 vs. 5.7 days; P = 0.02). CONCLUSION: We found a higher diagnostic specificity and accuracy of ¹⁸F-FDG-PET/CT compared to CT for detecting cancer in patients with NSSC. ¹⁸F-FDG-PET/CT should therefore be considered as first line imaging in this group of patients.