Can full-dose contrast-enhanced CT be omitted from an FDG-PET/CT staging examination in newly diagnosed FDG-avid lymphoma?

Objective: To determine whether full-dose contrast-enhanced computed tomography (CT) (CECT) can be omitted from an F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) (FDG-PET)/CT staging examination in newly diagnosed FDG-avid lymphoma.

Methods: Twenty-nine patients with newly diagnosed FDG-avid lymphoma prospectively underwent unenhanced low-dose FDG-PET/CT and CECT. Different observers evaluated unenhanced low-dose FDG-PET/CT and CECT in a blinded manner. Ann Arbor stages according to unenhanced low-dose FDG-PET/CT and CECT were compared, and discrepancies between the 2 imaging modalities were resolved using bone marrow biopsy and posttreatment FDG-PET/CT as reference standard. Finally, it was assessed as to how many cases therapy would have been changed based on additional CECT findings.

Results: In 27 of 29 patients (93%; 95% confidence interval, 78%-98%), CECT either did not change or did not correctly change the Ann Arbor stage that was assigned according to unenhanced low-dose FDG-PET findings. In 2 of 29 patients (7%; 95% confidence interval, 2%-22%), CECT correctly provided another Ann Arbor stage than unenhanced low-dose FDG-PET/CT. In the latter 2 cases, therapy would not have been changed based on additional CECT findings.

Conclusions: Unenhanced low-dose FDG-PET/CT alone is suggested as the primary imaging modality of choice for staging patients with newly diagnosed FDG-avid lymphoma. This diagnostic approach is particularly indicated in younger patients in whom diagnostic radiation exposure should be minimized and in patients who are at increased risk of CT contrast-induced allergic reactions or nephropathy.