POS0125 EXTRA-ARTICULAR FINDINGS WITH FDG-PET/CT IN RHEUMATOID ARTHRITIS PATIENTS: MORE HARM THAN BENEFIT.

Abstract

BackgroundWhole-body Positron Emission Tomography with CT-scanning using fluorine-18 fluorodeoxyglucose (18F-FDG) is occasionally used in Rheumatoid Arthritis (RA) patients. Reasons to use FDG-PET/CT-scans are to diagnose arthritis or guide decisions on systemic therapy, as FDG uptake in affected joints may reflect disease activity [1]. FDG-PET/CT might also detect malignancies, but the frequency of incidental findings and the proportion of relevant malignant disease that could be missed are currently unknown.ObjectivesTo study the malignancy screening performance of whole-body FDG-PET/CT in longstanding RA patients with low disease activity.MethodsFDG-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 Disease Modifying Anti-Rheumatic Drugs (bDMARDs) [3]. Baseline and if applicable follow up whole-body FDG-PET/CT-scans were performed in consenting patients in the tapering arm to assess predictive value of subclinical PET-arthritis for risk of flaring [4]. The scans were also read by experienced nuclear medicine specialists immediately after they were performed for any unexpected extra-articular finding, conform routine clinical care.The reference standard was clinical diagnosis of malignancy during the 3 year follow-up. Prevalence of extra-articular abnormalities, follow-up, and received treatments were summarized post-hoc.Results121 scans were made in 79 patients. Extra-articular abnormalities were found in 59/121 (48.8%) scans (Table 1) in 45/79 (57%) patients.Table 1.Abnormalities found on FDG-PET/CT scans# abnormal results found on scans (%)No PET/CT result obtained3 (2.5)No abnormalities found on any scan59 (48.8)One or more abnormalities found per scan*59 (48.8)Total number of scans121 Inflammatory7 (5.7) Suspected malignancies9 (7.4) Cardiovascular2 (1.6) Pulmonary7 (5.8) Gastrointestinal10 (8.3) Muscles/tendons3 (2.5) Bone-related3 (2.5) Hypermetabolic lymph nodes (non-specific)16 (13.2) Thyroid4 (3.3)* Fifteen of these abnormalities were found on the second PET/CT, the rest was found on the first scan. 11 abnormalities on the second PET/CT were the same as the one seen on the first scan, and 7 abnormalities resolved after the first scan. One scan can show multiple abnormalities, from different categories.Follow-up action occurred in 21 (26.6%) patients, consisting of referral to a specialist or reassessing and/or scheduling diagnostics directly by the treating rheumatologist. In 5 (6.3%) patients, the rheumatologist followed-up. In 17 (21.5%) patients a consultation with a different specialist was scheduled. In five patients surgical/invasive intervention took place. In one patient a hemi-thyroidectomy was performed revealing a follicular adenoma. This resection was complicated by persistent recurrent laryngeal nerve paresis and hoarseness. In a second, an intra-uterine myomectomy took place. In a third, a colonoscopy was performe revealing two low-grade adenomas. In a fourth a benign cyst in the neck was extracted. A fifth patient underwent spinal marginal myotomy which turned out to be a benign schwannoma.Nine patients (7.4%) were suspected of malignancy, none turned out to be malignant. Six clinical malignancies (bladder, penile, lymphoma, 2x melanoma and prostate) that developed during follow-up were all negative on baseline FDG-PET/CT. The malignancies were diagnosed after an interval of between 5 and 34 months (mean 13 months).ConclusionWhole-body FDG-PET/CT-scanning for arthritis imaging in RA patients results in frequent incidental extra-articular findings, while some who apparently had normal scans developed malignancies.