[18F]fluorodeoxyglucose uptake as a predictor of large joint destruction in patients with rheumatoid arthritis

Clinical features of atlantoaxial involvement in patients with rheumatoid arthritis using 18F-fluorodeoxyglucose-positron emission tomography with computed tomography

INTRODUCTION/OBJECTIVES

Cervical spine involvement is one of the most serious complications in rheumatoid arthritis (RA). The study aim was to assess the clinical significance of atlantoaxial (AA) joint involvement detected by ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) with computed tomography (CT) in patients with RA.

METHOD

A prospective cross-sectional study was conducted to evaluate AA joint involvement detected by FDG-PET/CT in consecutive RA patients from December 2017 to February 2022. We investigated the relationship between AA joint involvement and clinical data, including disease activity and patients' cervical symptoms.

RESULTS

Among 48 patients enrolled, abnormal FDG uptake at AA joint was detected in 13 (27%). Rheumatoid factor titre, initial disease activity score 28-erythrocyte sedimentation rate and total standardized uptake value were significantly higher in the 13 patients than in the others (P = 0.004, P < 0.001 and P = 0.001, respectively). All patients with abnormal FDG uptake at AA joint had some cervical symptoms regardless of cervical spine X-ray abnormalities. Neck pain on movement and at rest were more frequent in the 13 patients than in the others (P = 0.001 and P = 0.004, respectively). The most sensitive symptom associated with AA joint involvement was neck pain on movement (sensitivity, 69%), and the most specific symptom was neck pain at rest (specificity, 100%).

CONCLUSIONS

AA joint involvement was commonly observed by FDG-PET/CT in patients with active RA, independent of radiographic findings. Specific cervical symptoms can be important surrogate markers for detection of potential AA synovitis associated with active RA. Key Points • AA joint involvement was frequently seen in RA with high disease activity independent of radiographic findings. • Neck pain was a hallmark of AA joint involvement reflecting disease activity, and resting pain was highly specific.

[18F]FDG PET/CT in rheumatoid arthritis

[¹⁸F]fluorodeoxyglucose (FDG) PET/CT can be used to image the inflammation in rheumatoid arthritis. Specifically, the synovial metabolic activity can be evaluated visually and measured using standard uptake values. Fluorine-18-labeled Sodium fluoride (NaF) PET/CT can be used to determine synovial osteoblastic activity. Response assessment using FDG PET/CT is routine in many cancers and this is now an emerging technique for rheumatoid arthritis. Vasculitis in rheumatoid arthritis (RA) can be also studied with FDG PET/CT and aortic calcification with NaF PET/CT. These techniques could be useful in determining RA disease severity. FDG PET/CT is a useful technique to exclude underlying malignancy when RA does not follow the expected course. A number of novel tracers are being studied with regard to their applicability in rheumatoid arthritis and some of these could even be used in a theranostic manner in the future.

FDG PET-CT in rheumatological diseases

2-deoxy-2[¹⁸F]fluoro-D-glucose (FDG) PET-CT has revolutionized oncological imaging. The cellular processes that make cancer cells visible on FDG PET-CT also occur in a number of inflammatory cells. Exploiting this phenomenon has led to a growth of evidence supporting the use of FDG PET-CT in a wide range of infective and inflammatory diseases. Rheumatological diseases can affect multiple sites within the musculoskeletal system alongside multi-organ extra-articular disease manifestations. Inflammation is central to these diseases, making FDG PET-CT a logical choice. In this review article we describe the various applications of FDG PET-CT in rheumatological diseases using illustrative examples to highlight the beneficial role of FDG PET-CT in each case.

Do biologic therapies reduce aortic inflammation in rheumatoid arthritis patients?

Objectives

Rheumatoid arthritis (RA) patients have an increased risk of cardiovascular disease (CVD). In the present study, we evaluated the inflammatory activity of the ascending aorta in RA patients who received biological treatment.

Methods

We assessed the aortic wall inflammation of RA patients using ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography before and after 6 months of biologic therapies. We also compared the inflammatory activity at the aortic wall in RA patients with remission or low disease activity (RLDA) and those with moderate or high disease activity (MHDA). The aortic uptake was measured by the standardized uptake value (SUV) and the target-to-background ratio (TBR).

Results

A total of 64 patients were included in the analysis (mean age, 58.4 ± 13.8 years old; female, 77%). The Disease Activity Score for 28 joints (DAS28) erythrocyte sedimentation rate (ESR) had significantly decreased after 6 months: from 5.0 ± 1.2 to 3.3 ± 1.2 (p < 0.001). The FDG uptake in the ascending aorta changed from baseline to 6 months, showing a maximum SUV (SUV_max) of 1.83 ± 0.34 to 1.90 ± 0.34 (p = 0.059) and TBR of 1.71 ± 0.23 to 1.75 ± 0.24 (p = 0.222). The SUV_max and TBR after 6 months were significantly higher in the RLDA group than in the MHDA group (2.05 ± 0.32 vs. 1.79 ± 0.33 (p = 0.002) and 1.89 ± 0.33 vs. 1.65 ± 0.20 (p = 0.001), respectively). The percentage of monocytes also significantly increased from baseline to 6 months: from 5.9 ± 1.6 to 6.9 ± 2.6 (p = 0.032).

Conclusion

The inflammation activity at the ascending aorta in RA patients did not change significantly after 6 months of biological treatment. RA patients with a low disease activity or in clinical remission after 6 months of biological treatment still had an increased inflammatory activity at the aortic wall.

Does periodontitis affect the treatment response of biologics in the treatment of rheumatoid arthritis?

BACKGROUND

Rheumatoid arthritis (RA) and periodontitis (PD) have been suggested to share many clinical and pathological features. However, few reports have investigated the relationship between the degree of PD and the treatment response to RA. This study aimed to examine the relationship between the extent of PD and the treatment response to biologics in RA patients using FDG-PET/CT.

METHODS

Sixty RA patients (male, n = 14; female, n = 46; average age, 58.3 years) treated with biologic agents were included in this study. FDG-PET/CT was performed at baseline and 6 months after the initiation of biological therapy. The maximum standardized uptake value (SUVmax) was used as a representative value for the assessment of the FDG uptake in periodontal tissue and joints including the bilateral shoulders, elbows, wrists, hip, knees, and ankle joints. The Disease Activity Score (DAS) 28-CRP and the following clinical parameters were assessed: C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), anti-cyclic citrullinated peptide antibody (ACPA), rheumatoid factor (RF), and matrix metalloproteinase 3 (MMP-3). The relationship between the treatment response of RA and the baseline SUVmax of the periodontal tissue was evaluated.

RESULTS

The baseline periodontal SUVmax was related to patient age (r = 0.302, p = 0.009) and the ACPA level (r = 0.265, p = 0.025). The DAS28-CRP, CRP, ESR, MMP-3, and joint SUVmax values were significantly decreased after 6 months of biological therapy. However, the mean periodontal SUVmax, ACPA, and RF showed no significant changes after treatment. There was a significantly negative correlation between the baseline periodontal SUVmax and the treatment response of DAS28-CRP (r = - 0.369, p = 0.004).

CONCLUSION

There was a negative correlation between the extent of PD at baseline and the treatment response of RA patients who received biological therapy. The evaluation of the periodontal condition is considered to be an essential part for the management of RA.

Shoulder tenderness was associated with the inflammatory changes on magnetic resonance imaging in patients with rheumatoid arthritis

The aim of this study was to assess the association between the shoulder tenderness and the inflammatory changes on magnetic resonance imaging (MRI) in the rheumatoid shoulder. Forty-one shoulders of 41 patients with rheumatoid arthritis (RA) were examined. We evaluated synovitis, erosion and bone marrow edema, by counting the numbers of each positive site, and rotator cuff tears on shoulder MRI. The association between the shoulder tenderness and the MRI findings were statistically analyzed. Twenty-three of 41 patients had tenderness in the shoulder joints. There were 20 shoulders (48.8%) with rotator cuff tear, and no significant difference was observed in the prevalence of rotator cuff tear between the tenderness group and non-tenderness group (p = 0.080). There were no significant differences in the demographic data between these two groups. In MRI findings, we found significant difference for the synovitis (p = 0.001) and bone marrow edema (p = 0.021). Synovitis was strongly associated with the shoulder tenderness (OR: 3.996, 95% CI: 1.651-9.671). Synovitis was the factor most associated with shoulder tenderness.

Comparison of methods of quantifying global synovial metabolic activity with FDG-PET/CT in rheumatoid arthritis

AIM

2-deoxy-2-[¹⁸ F]fluoro-d-glucose positron emission tomography/computed tomography (FDG-PET/CT) can portray increased glycolysis due to inflammation in rheumatoid arthritis (RA). The aim of this study was to evaluate and compare the reliability and construct validity of two methods of quantifying RA disease activity using FDG-PET/CT.

METHOD

Nineteen RA patients and 19 healthy controls matched to sex and age underwent prospective FDG-PET/CT imaging. Metabolic and volumetric metrics were calculated using fixed and adaptive thresholding techniques and partial volume correction. Fixed thresholds segmented regions above average maximum physiological uptake in controls. Differences of means between RA and controls were assessed using t tests, and discrimination was assessed using receiver operating characteristics. Spearman correlation analysis was used to assess associations between FDG-PET/CT measures and clinical assessments of disease activity.

RESULTS

All FDG-PET/CT measures were substantially different and nearly non-overlapping between RA and controls (all P < .001). Area under the curve (AUC) for adaptive threshold parameters ranged from 0.986 to 0.997, and AUC for fixed threshold parameters ranged from 0.898 to 0.945. PET parameters were found to correlate positively with various clinical features, namely C-reactive protein, erythrocyte sedimentation rate, interleukin (IL)-6, IL-1, and swollen joint count.

CONCLUSION

All FDG-PET/CT parameters reflecting global RA disease activity differentiated between RA and controls, indicating high clinical utility to diagnose and assess RA. Adaptive thresholds can be used in a wider setting without control data, but methods utilizing fixed thresholds were more reproducible and more closely associated with indications of inflammation.

Axillary lymph-node metabolic activity assessment on 18F-FDG-PET/CT in rheumatoid arthritis patients treated with biologic therapies

Objective: Recent studies have provided new insights into the role of lymph nodes (LNs) in rheumatoid arthritis (RA). The aim of this study was to evaluate the metabolic activity of the axillary LNs in relation to that of the upper limb joints and the clinical assessment of disease activity in RA patients treated with biologic therapies.Method: ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) scans were acquired for 64 patients with RA at baseline and after 6 months of biologic therapy, and the patients' clinical status was evaluated. The maximum standardized uptake value (SUV_max), metabolic active volume, and total lesion glycolysis (TLG) were used to assess glucose metabolism in the LNs and 12 joints. Clinical evaluations included serum markers and the Disease Activity Score based on 28-joint count-erythrocyte sedimentation rate (DAS28-ESR).Results: Changes in the SUV_max and TLG for the axillary LNs correlated significantly with those of the ipsilateral wrist joints. There was a positive correlation between the changes in the three metabolic parameters of the axillary LNs and the changes in disease activity after treatment. After 6 months of biologic therapy, all metabolic parameters for the axillary LNs in patients with a DAS28-ESR < 3.2 were significantly lower than those of patients with a DAS28-ESR ≥ 3.2.Conclusion: A relationship between the glucose metabolism of the axillary LNs and the ipsilateral wrist joints was demonstrated by the ¹⁸F-FDG-PET/CT parameters. The metabolic activity and active volume of axillary LNs may reflect the therapeutic response to the biologic treatment of RA.

Quantitative Metabolic Volumetric Product on 18Fluorine-2fluoro-2-deoxy-D-glucose-positron Emission Tomography/Computed Tomography in Assessing Treatment Response to Disease-modifying Antirheumatic Drugs in Rheumatoid Arthritis: Multiparametric Analysis Integrating American College of Rheumatology/European League Against Rheumatism Criteria

The purpose of this study was to assess the role of fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) in the evaluation of treatment response evaluation to disease-modifying antirheumatic drug (DMARD) therapy in patients of rheumatoid arthritis (RA). A total of ten patients with proven diagnosis of RA as per the 2010 American College of Rheumatology/European League against Rheumatism (EULAR) criteria were prospectively evaluated. All patients underwent clinical and biochemical evaluation and a baseline FDG-PET/CT with assessment of maximum standardized uptake value and metabolic volumetric product (MVP) values. DMARD therapy was started with a combination of hydroxychloroquine and sulfasalazine. On follow-up at 3 and 6 months, the response to treatment was assessed by clinical, biochemical, and FDG-PET/CT parameters. These parameters were analyzed in a combined manner, and the patients were grouped into 4 categories as per response to DMARD therapy - complete response, good response, mixed response, and no response. Evaluation of treatment response in ten patients at 3^rd month and in nine patients at 6 months showed (a) agreement for MVP, biochemical parameters with clinical symptomatic assessment in all patients, (b) while agreement for EULAR score was noted in only three patients and disagreement in seven patients with clinical symptoms Response EULAR (rEULAR) (0.37) and at 6 months in only three patients and disagreement in six patients, rEULAR (0.52). The correlation factors at 3^rd month and 6^th months were, respectively, as follows: rMVP (0.67 and 0.75), response RA factor (0.54 and 0.74), response erythrocyte sedimentation rate (0.81 and 0.73), response C-reactive protein (0.78 and 0.51), and response anti-cyclic citrullinated peptide antibodies (0.33 and 0.54). The overall response to DMARD therapy at 3 months was assessed with results showing good response by four cases (40%), mixed response by 1 (10%), no response by 5 (50%), and complete response by none (0%). Step-up therapy at 3 months was initiated in four patients showing nonresponse/progression on clinical symptomatic assessment; of these, two patients showed a good response, one mixed response, and the remaining one continued to show nonresponse at 6 months follow-up. One patient who had a minimal response at 3 months on PET-CT (only 5.96% reduction of MVP) was continued on the same DMARD in view of clinical symptomatic good response (at 3 months) but ultimately had disease progression in all scales and worsening of symptom (at 6 months). FDG-PET/CT-based assessment of inflammatory activity noted in the joints of RA with quantitative parameters can be a promising approach for the whole body assessment of RA disease activity and treatment response assessment, especially in inconclusive cases and correlates well with other parameters. MVP can be used as a useful objective and adjunct parameter for assessing response to treatment.

Predictive factors related to shoulder joint destruction in rheumatoid arthritis patients treated with biologics: A prospective study

OBJECTIVE

The aim of this study was to assess the risk factors for shoulder joint destruction in rheumatoid arthritis (RA) patients treated with biologics.

METHODS

Thirty shoulders of 29 patients with RA were assessed using 18F-fluorodeoxyglucose positron emission tomography (PET) and magnetic resonance imaging (MRI) before starting biologics and 6 months later. The mean age (range) was 54 (18-72) years, and the mean disease duration was 7 (0.8-30) years. The radiographic findings were assessed at baseline and 3 years later. The inflammation markers and RA disease activity were also assessed. These parameters were compared between the progression of joint destruction group and the no progression group.

RESULTS

The SUVmax on PET, the rate of synovitis, and the rate of rotator cuff tear on MRI before biologic treatment were significantly higher in the progression of joint destruction group. SUVmax and synovitis on MRI after 6 months were also significantly higher in the progression of joint destruction group. On logistic regression analysis, the SUV at baseline of the shoulder joint was the main risk factor for joint destruction.

CONCLUSION

The detection of synovitis by imaging was more important than disease activity and inflammation markers for assessing the progression of shoulder joint destruction.

Effect of total knee arthroplasty on other joints in patients with rheumatoid arthritis evaluated by 18-FDG-PET

AIM

The objective of this study was to assess arthritis of the whole body before and after total knee arthroplasty (TKA) in patients with rheumatoid arthritis (RA) using positron emission tomography (PET).

METHOD

Seventeen knees of 17 RA patients (median age 68 years) who underwent TKA were included in this study. Clinical assessments of disease activity, knee function and activities of daily living (ADL) were performed before and after TKA. ¹⁸ Fluorodeoxyglucose (FDG)-PET was performed preoperatively and 12 weeks postoperatively when RA disease activity was assessed. The maximal standardized uptake value (SUV) in the region of interest was used to assess FDG uptake.

RESULTS

Disease activity and knee function improved in all patients after TKA. There was a significant decrease in the number of patients with swollen or tender joints involving the right wrist, right knee and left knee. The SUV of bilateral wrist joints decreased significantly 12 weeks after TKA, whereas the SUVs of other large joints were unchanged.

CONCLUSION

TKA can improve not only ADL and knee function, but also the disease activity index in RA patients. However, TKA has limited effectiveness against synovitis of the joints not undergoing surgery.