18F-FDG-PET/CT vs CT in Cancer Detection

Imaging with 18F-FDG-PET/CT compared to CT for detecting cancer in patients with nonspecific signs and symptoms of cancer (NSSC) provides a higher diagnostic specificity and accuracy than does CT alone, according to a study published in The Journal of Nuclear Medicine.

Researchers from Denmark conducted a randomized prospective trial of patients with serious NSSC symptoms to determine if 18F-FDG-PET/CT was superior to CT as initial imaging modality in this patient group.

Two-hundred patients participated in the trial, 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 were available for 197 patients.

Diagnosis following examination included:

• 39 patients (20%) were diagnosed with cancer

• 10 (5%) with an infection

• 15 (8%) with an autoimmune disease

• 76 (39%) with other diseases

• 57 patients (28%) no specific disease found

“Compared to CT scans, 18F-FDG-PET/CT had a higher specificity (96% versus 85%) and a higher accuracy (94% versus 82%),” the authors wrote. “However, there were no statistically significant differences in sensitivity (83% versus 70%) or negative predictive values (96% versus 92%).”

The researchers found no difference could be shown in days to final referral diagnosis in the randomization group (7.2 days compared with 7.6 days), but 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 compared with 5.7 days).

The researchers concluded that there was 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.