Extra-articular findings with FDG-PET/CT in rheumatoid arthritis patients: more harm than benefit

Whole-body PET with CT scanning using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) is used occasionally in RA patients to detect arthritis. FDG-PET/CT might also detect malignancies, but the amount of incidental findings and the number of relevant malignant diseases that could be missed are currently unknown. We aimed to study the malignancy screening performance of whole-body FDG-PET/CT in longstanding RA patients with low disease activity.

FDG-PET/CT scanning was done in the intervention arm of the Dose REduction Strategy of Subcutaneous TNF-inhibitors (DRESS) study, a randomized controlled trial on dose-tapering of biological DMARDs. The reference standard was clinical diagnosis of malignancy during the 3-year follow-up period of the study. Prevalence of extra-articular abnormalities, follow-up and treatments were summarized post hoc.

One hundred and twenty-one scans were carried out in 79 patients. Extra-articular abnormalities were found in 59 of 121 (49%) scans, resulting in additional diagnostic procedures in 21 of 79 (26.6%) patients. Nine patients (7.4%) were suspected of malignancy; none turned out to be malignant. Six clinical malignancies that developed during follow-up were all negative on baseline FDG-PET/CT.

Whole-body FDG-PET/CT scanning used in RA patients for imaging of arthritis results in frequent incidental extra-articular findings, whereas some who apparently had normal scans also developed malignancies.

Netherlands Trial Register, www.trialregister.nl, NL6771.