Value of 18F-FDG PET/CT for therapeutic assessment of patients with polymyalgia rheumatica receiving tocilizumab as first-line treatment

[18F]FDG-PET/CT in Polymyalgia Rheumatica: An Update and Future Aspects

Polymyalgia rheumatica (PMR) is an inflammatory disorder usually diagnosed in patients older than 50 years of age. It is characterized by sudden onset pain and prolonged morning stiffness in the scapular and/or pelvic girdle, sometimes debilitating and accompanied by constitutional symptoms such as weight loss. In approximately 20% of the cases, it is linked to giant cell arteritis (GCAV) representing a disease continuum. The diagnosis is mainly clinical and noninvasive imaging such as ultrasound of joints may be helpful. In atypical PMR cases, whole body imaging using [18F]FDG-PET/CT may be useful. First, to confirm or rule out the diagnosis of PMR, secondly, to assess the coexistence of a GCA, and thirdly to establish the differential diagnosis with other types of arthritides encountered in this age group, such as elderly-onset rheumatoid arthritis, spondyloarthropathies, crystal-induced arthropathies or the rare remittent seronegative symmetrical synovitis with pitting edema. Relatively typical patterns of [18F]FDG-PET/CT are well known, based on the clinical distribution of the disease (eg, scapular and pelvic girdle, interspinous bursae, sterno-costoclavicular joints, entheses), especially the hypermetabolism at the interspinous lumbar bursae that has shown the best post-test likelihood ratio in a meta-analysis. This article focuses on the differential diagnosis and on the visual and semi-quantitative tools that can be used to guide to the correct diagnosis of PMR as an add-on to the clinical picture. Further, we briefly discuss the options that can improve molecular imaging in the future for inflammatory rheumatisms in elderly.

[18F]FDG PET/CT for therapeutic assessment of Abatacept in early-onset polymyalgia rheumatica

PURPOSE

Evaluate the benefit of 2-deoxy-2-[18F]-fluoro-D-glucose ([18F] FDG) positron emission tomography/computed tomography (PET/CT) for the therapeutic assessment of Abatacept (ABA) as first-line therapy in early-onset polymyalgia rheumatica (PMR) patients.

METHODS

This was an ancillary study of ALORS trial (Abatacept in earLy Onset polymyalgia Rheumatica Study) assessing the ability of ABA versus placebo to achieve low disease activity (C-Reactive Protein PMR activity score (CRP PMR-AS) ≤ to 10) without glucocorticoid (GC) at week 12 in patients with early-onset PMR. The patients underwent [18F] FDG PET/CT at baseline and after 12 weeks of treatment. Responses to treatments were evaluated according to CRP PMR-AS, Erythrocyte Sedimentation Rate (ESR) PMR-AS, Clin PMR-AS, and CRP-Imputed (Imput-CRP) PMR-AS. Quantitative score by maximal standardized uptake value (SUVmax) and combined qualitative scores according to liver uptake (Leuven, Leuven/Groningen, and Besançon Scores) were used for assessment of [18F] FDG uptake in regions of interest (ROI) usually affected in PMR. Student's t-test was applied to evaluate the clinical, biological, and [18F] FDG uptake variation difference in ABA and placebo groups between W0 and W12. Subgroup analysis by GC rescue was performed.

RESULTS

At W12, there was no significant difference according to SUVmax between the ABA and the placebo groups in all ROI. Subgroup analysis according to GC administration demonstrated a significant (p 0.047) decrease in SUVmax within the left sternoclavicular joint ROI in the ABA group (- 0.8) compared to the placebo group (+ 0.6) without GC rescue. Other results did not reveal any significant difference between the ABA and placebo groups. According to combined qualitative scores, there was no significant difference between ABA and placebo groups for the direct comparison analysis and subgroup analysis according to GC rescue.

CONCLUSION

[18F] FDG PET/CT uptake did not decrease significantly after ABA compared to placebo in anatomical areas usually affected in PMR patients. These results are correlated with the clinical-biological therapeutic assessment.

CLINICAL TRIAL REGISTRATION

The study was approved by the appropriate ethics committee (CPP Sud-Est II Ref CPP: 2018-33), and all patients gave their written informed consent before study enrollment. The protocol was registered on Clinicaltrials.gov (NCT03632187).

Decoding polymyalgia rheumatica, the role of Nuclear Medicine Imaging

Polymyalgia rheumatica (PMR) is an inflammatory joint disease that presents in patients older than 50 years with prolonged morning pain and stiffness in the shoulder and hip joints and neck. The lack of specific clinical findings, laboratory signs, biomarkers and established imaging methods makes it difficult to diagnose patients with this disease. 18F-FDG PET/CT is a functional imaging technique that is an established tool in oncology and has also proven useful in the field of inflammatory diseases. The aim of this paper is to present literature evidence on the use of molecular imaging methods such as PET/CT for early diagnosis, assessment of disease activity and therapeutic response in PMR. At the same time, the advantages, disadvantages and contraindications of other methods are considered.

Case Report and Literature Review of an Atypical Polymyalgia Rheumatica and Its Management

Polymyalgia rheumatica (PMR) is a systemic inflammatory disease of the elderly population that increases in incidence as age advances. It is characterised by the sudden or sub-acute onset of symptoms affecting the shoulder and pelvic girdles, often accompanied by constitutional symptoms. Due to the lack of consensual diagnostic criteria and specific laboratory or radiological investigations for PMR, its diagnosis can be very challenging, particularly because it can be mimicked or masked by other geriatric syndromes. PMR responds well to glucocorticoid treatment, but if left untreated, can lead to morbidity and poor quality of life. We present the case of an 87-year-old male who presented with a one-week history of localised pain in the left hip joint, later involving the contralateral hip. Previously able to ambulate unaided, his mobility was now severely impaired. Due to his Alzheimer's dementia and multiple comorbid geriatric conditions, extensive investigations were undertaken before a diagnosis of atypical PMR was reached. Treatment with a low dose of prednisolone led to a full recovery. This case highlights the inconsistency between an atypical presentation and the classic presentation of PMR and draws attention to the possibility of missed diagnosis in older, frail patients. Atypical symptomatology on top of cognitive impairment and language barriers can be easily overlooked and left untreated and could lead to severe adverse outcomes. Accurate diagnosis is crucial, as PMR is readily diagnosed, but the treatment with glucocorticoids, though generally straightforward, can pose challenges, particularly when dealing with polypharmacy and multiple coexisting health conditions.

Polymyalgia rheumatica

Polymyalgia rheumatica is an inflammatory disease producing pain and stiffness, mainly in the shoulders and pelvic girdle, in people older than 50 years. Elevation of acute phase reactants is common due to the inflammatory nature of the disease. Since there are no specific diagnostic tests, diagnosis requires the exclusion of other diseases with similar presentations. Imaging has helped to identify the pathological substrate of polymyalgia rheumatica and it is increasingly used to support clinical diagnosis or to detect coexistent giant cell arteritis. Although polymyalgia rheumatica does not clearly impair survival or organ function, it can have a detrimental effect on quality of life. Glucocorticoids at 12·5-25·0 mg prednisone per day are effective in inducing remission in most individuals but, when tapered, relapses occur in 40-60% of those affected and side-effects are common. Assessment of disease activity can be difficult because pain related to common comorbidities such as osteoarthritis and tendinopathies, can return when glucocorticoids are reduced, and acute phase reactants are increased less during flares in individuals undergoing treatment or might increase for other reasons. The role of imaging in assessing disease activity is not yet completely defined. In the search for more efficient and safer therapies, tocilizumab and sarilumab have shown efficacy in randomised controlled trials and additional targeted therapies are emerging. However, judicious risk-benefit balance is essential in applying therapeutic innovations to people with polymyalgia rheumatica.

Biological therapy in polymyalgia rheumatica

INTRODUCTION

Polymyalgia rheumatica (PMR) is an inflammatory rheumatic disease of the elderly, treated mainly with systemic corticosteroids. The frequency of side effects of steroids is high in this aged population and increased due to comorbidities. The use of biological treatments could be of interest in this condition.

AREAS COVERED

This review takes into account literature data from the PubMed and clinical trial databases concerning the results of the use of biological treatments in PMR, in terms of efficacy and safety of these treatments.

EXPERT OPINION

Current data do not allow us to identify any particular efficacy of the various anti-TNF agents used in the treatment of PMR. Anti-interleukin 6 agents (tocilizumab, sarilumab) have shown consistent efficacy results, suggesting a particularly interesting steroid-sparing effect in the population under consideration. The safety profile appears acceptable. Other biologic targeted treatments are currently being evaluated. Anti-interleukin-6 agents may well have a place in the therapeutic strategy for PMR, particularly for patients with steroid-resistant disease or at high risk of complications of corticosteroid therapy.

Steroid-sparing agents in polymyalgia rheumatica: how will they fit into the treatment paradigm?

INTRODUCTION

Polymyalgia rheumatica is a common inflammatory rheumatic disease in subjects aged 50 years or older and classically presents with shoulder and/or pelvic girdle pain and prolonged morning stiffness. Glucocorticoids represent the standard of treatment; glucocorticoid therapy is usually required for 1-2 years and often results in significant glucocorticoid-related side effects, especially in the elderly.

AREAS COVERED

In this review, we aimed to provide a comprehensive overview of the management of polymyalgia rheumatica, with a particular focus on adjunctive therapies to the standard glucocorticoid treatment.

EXPERT OPINION

Given the high frequency of disease relapses (one-third of patients) and the adverse events related to prolonged glucocorticoid use, the need for glucocorticoid-sparing agents remains an important issue in the management of polymyalgia rheumatica. In selected patients, who are at risk for glucocorticoid-related side effects or in those with glucocorticoid-refractory disease, the addition of a glucocorticoid-sparing agent, either a synthetic or biologic disease-modifying anti-rheumatic drug, may represent a reasonable and effective therapeutic approach.

[Methods for assessment of disease activity of polymyalgia rheumatica]

Polymyalgia rheumatica (PMR) is the second most frequent inflammatory rheumatic disease in old age. Remission and recurrence are frequently used as endpoints in clinical trials; however, there is as yet no international consensus on the definition of these states, which limits the comparability of published studies. The PMR activity score (PMR-AS) is the only composite score specifically developed for PMR, which together with remission is used to define low, middle and high disease activity. In recent studies the PMR-AS was often used and low disease activity was established as endpoint. The most important limitation of the PMR-AS is the potential influence of the individual variables by comorbidities. The value of C‑reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) are of restricted value in studies using drugs that influence the interleukin 6 (IL-6) axis. In these cases, calprotectin and osteopontin are promising alternative biomarkers, as they have already been shown to reflect disease activity independently of CRP in rheumatoid arthritis. Furthermore, imaging modalities including sonography, magnetic resonance imaging and fluorodeoxyglucose (FDG) positron emission tomography could also be helpful in monitoring disease activity; however, these techniques must first be validated in further studies. The PMR impact scale (PMR-IS) is a composite score to assess the impact of PMR on the patients; however, it has not yet been used in clinical studies. The development of additional patient reported outcomes (PRO) for PMR and the definition of standardized criteria for documentation of remission and recurrence are important questions in the future research agenda for PMR.

Usefulness of 18F-Fluorodeoxyglucose Positron Emission Tomography in Diagnosing Polymyalgia Rheumatica and Large-Vessel Vasculitis: A Case-Control Study

INTRODUCTION

We aimed to evaluate the utility of FDG-PET/CT in diagnosing polymyalgia rheumatica (PMR) and associated large-vessel vasculitis (LVV).

METHODS

We analyzed FDG-PET/CT completed between 2015 and 2019 on patients diagnosed with PMR. For comparisons, patients with PMR were matched 1:1 to controls based on age and gender. FDG-PET/CT had been completed on the controls over the same period. The FDG uptake was scored visually for 17 articular or periarticular sites and 13 vascular sites using a semi-quantitative scoring system (score of 0-3).

RESULTS

Eighty-one patients with PMR and eighty-one controls were included (mean age 70.7 (9.8) years; 44.4% women). Significant differences between the PMR and control groups were found at all articular and periarticular sites for the following: (i) the FDG uptake score (p < 0.001 for all locations); (ii) the number of patients per site with significant FDG uptake (score ≥ 2); (iii) the global FDG articular uptake scores (31 [IQR, 21 to 37] versus 6 [IQR, 3 to 10], p < 0.001); and (iv) the number of sites with significant FDG uptake (score ≥ 2) (scores of 0-17) (11 [IQR, 7 to 13] versus 1 [IQR, 0 to 2], p < 0.001). No significant differences in the global FDG vascular uptake scores were found between the patients who were considered isolated PMR and the control groups.

CONCLUSIONS

The FDG uptake score and the number of sites with significant FDG uptake could be pertinent criteria for the diagnosis of PMR. Unlike others, we did not confirm the presence of vascular involvement in patients with isolated PMR.

Role of 18F-FDG PET/CT in Large Vessel Vasculitis and Polymyalgia Rheumatica

Systemic vasculitides comprise a group of autoimmune diseases affecting blood vessels, including large vessel vasculitis (LVV) and medium-sized vessel vasculitis such as giant cell arteritis (GCA) and Takayasu arteritis (TAK). GCA frequently overlaps with polymyalgia rheumatica (PMR), a rheumatic inflammatory condition affecting bursae, tendons or tendon sheaths, and joints. ¹⁸F-FDG PET/CT plays an important role in the diagnostic work-up of GCA, PMR, and TAK and is increasingly used to monitor treatment response. This continuing education article provides up-to-date guidance on the role of ¹⁸F-FDG PET/CT in patients with LVV, medium-sized vessel vasculitis, and PMR. It provides a general introduction on the clinical presentation and challenges in the diagnostic work-up of LVV and medium-sized vessel vasculitis, with a focus on the 2 major LVV subtypes: GCA, including PMR, and TAK. Next, practice points to perform and interpret the results of ¹⁸F-FDG PET/CT are described in line with the published procedure recommendations. Furthermore, the diagnostic performance and its role for treatment monitoring are discussed, taking into account recent international recommendations for the use of imaging in LVV and medium-sized vessel vasculitis in clinical practice. This is illustrated by several clinically representative PET/CT scan examples. Lastly, knowledge of limitations and pitfalls is essential to understand the role of ¹⁸F-FDG PET/CT in LVV, medium-sized vessel vasculitis, and PMR. Challenges and opportunities, as well as future research and conclusions, are highlighted. Learning objectives provide up-to-date guidance for the role of ¹⁸F-FDG PET/CT in patients with suspected LVV, medium-sized vessel vasculitis, and PMR.

Imaging methods in polymyalgia rheumatica: a systematic review

Polymyalgia rheumatica (PMR) is an inflammatory joint disease in patients over 50 years of age with pain and prolonged morning stiffness in the shoulder and hip girdles and neck. The lack of specific clinical findings, laboratory signs, biomarker and established imaging methods makes it difficult to diagnose patients with this disease. The aim of the systematic review is to present the literature data on the use of imaging methods for early diagnosis, assessment of disease activity and therapeutic response in PMR. At the same time, the advantages, disadvantages and contraindications of each method are considered. A literature search was carried out in PubMed and Scopus up to June 2022. Studies were selected that met the following criteria: (1) English language publications in peer-reviewed journals, (2) cohort or case-control studies and a series of more than five clinical cases, (3) studies of newly diagnosed or suspected PMR patients according to classification criteria or expert opinion, (4) imaging evaluation of articular, extraarticular and vascular impairment in PMR. Out of a total of 1431 publications, 61 articles were selected, which differed in the imaging techniques used: radiography (5), scintigraphy (4), magnetic resonance imaging (14), PET/CT (14) and ultrasound (24). Prevalence of extraarticular involvement (tendons, entheses and bursae) was identified in patients with PMR. In a significant number of cases, subclinical vasculitis of the large vessels was found, confirming the common pathogenetic pathways of the two diseases. The diagnostic, therapeutic and prognostic potential of imaging methods in PMR has been relatively poorly studied and remains to be clarified.

18F-FDG PET molecular imaging: A relevant tool to investigate chronic inflammatory rheumatisms in clinical practice?

18F-Labeled Fluorodeoxyglucose-Positron Emission Tomography (18F-FDG PET) is a molecular imaging tool commonly used in practice for the assessment of many cancers. Thanks to its properties, its use has been progressively extended to numerous inflammatory conditions, including chronic inflammatory rheumatism (CIR) such as rheumatoid arthritis (RA), spondylarthritis (SpAs) and polymyalgia rheumatica (PMR). 18F-FDG PET is currently not recommended for the diagnostic of CIRs. However, this whole-body imaging tool has emerged in clinical practice, providing a general overview of systemic involvement occurring in CIRs. Numerous studies have highlighted the capacity of 18F-FDG PET to detect articular and extra articular involvements in RA and PMR. However, the lack of specificity of 18F-FDG limits its use for diagnosis purpose. Finally, the key question is the definition of the best way to integrate this whole-body imaging tool in the patient's management workflow.

Diagnostic accuracy and validation of 18F-fluorodeoxyglucose positron emission tomography scores in a large cohort of patients with polymyalgia rheumatica

Background

Several studies have shown that ¹⁸F-FDG PET may contribute to the diagnosis of polymyalgia rheumatica (PMR). Previously, we developed a composite PET score called the Leuven score, which was recently adapted to the more concise Leuven/Groningen score by van der Geest et al. The aim of this study is to validate and compare the diagnostic accuracy and cut-off points of both scores in a large cohort of PMR patients.

Methods

Patients with a possible clinical diagnosis of PMR and a PET scan prior to the initiation of glucocorticoids between 2003 and 2020 were included retrospectively. The gold standard for the diagnosis of PMR was the judgment of two experienced clinicians after a follow-up of at least 6 months. FDG uptake was scored visually in 12 articular regions (scores 0–2) and a total skeletal score was calculated by summing the individual scores (maximum of 24 for the Leuven score and 14 for the Leuven/Groningen score). Receiver operating characteristic (ROC) analysis and the Youden index were used to determine the diagnostic accuracy and optimal cut-off points.

Results

A total of 162 patients with PMR and 83 control patients were included. Both PET scores showed high diagnostic accuracy in the ROC analysis (area under the curve 0.986 and 0.980, respectively). The Leuven Score provided a sensitivity of 91.4%, specificity of 97.6% and accuracy of 93.5% at its predefined cut-off point of 16. With the newly determined cut-off point of 12 the sensitivity was 98.8%, the specificity 95.2% and the accuracy 97.6%. The Leuven/Groningen score had a sensitivity, specificity and accuracy of 93.2%, 95.2%, and 93.9%, respectively, with the pre-specified cut-off point of 8, and 96.9%, 92.8%, and 95.5% with the optimal cut-off point of 7.

Conclusion

The original Leuven score and the simplified Leuven/Groningen score both had excellent diagnostic accuracy. The latter may be easier to apply in clinical practice.

Effect of Tocilizumab on Disease Activity in Patients With Active Polymyalgia Rheumatica Receiving Glucocorticoid Therapy: A Randomized Clinical Trial

IMPORTANCE

Few treatments are available for patients with glucocorticoid-dependent polymyalgia rheumatica. IL-6 antagonists may reduce disease activity in patients with active glucocorticoid-dependent polymyalgia rheumatica.

OBJECTIVE

To compare the efficacy of tocilizumab vs placebo in patients with glucocorticoid-dependent polymyalgia rheumatica.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind, parallel-group, placebo-controlled randomized clinical trial enrolled 101 patients with polymyalgia rheumatica at 17 hospitals in France from February 2017 to October 2019. Final follow-up occurred in November 2020. Inclusion criteria were persistent disease activity (polymyalgia rheumatica activity score computed using the C-reactive protein level [CRP PMR-AS] >10) and prednisone dose greater than or equal to 10 mg per day.

INTERVENTIONS

Patients were randomly assigned to receive intravenous tocilizumab (8 mg/kg; n = 51) or placebo (n = 50) every 4 weeks for 24 weeks, combined with predefined standardized tapering of oral prednisone.

MAIN OUTCOMES AND MEASURES

The primary efficacy end point was CRP PMR-AS less than 10 (range, 0-100; higher values indicate greater activity; no minimal clinically important difference defined) combined with either prednisone dose less than or equal to 5 mg per day or a decrease in prednisone dose greater than or equal to 10 mg from baseline at week 24. There were 11 secondary outcomes assessed at week 24 included in this report, including disease activity (measured by CRP PMR-AS) and the proportion of patients no longer taking prednisone.

RESULTS

Of the 101 randomized patients (mean age, 67.2 years; 68 [67.3%] women), 100 (99%) received at least 1 infusion and 100 completed the trial. The primary end point was achieved in 67.3% of patients in the tocilizumab group and 31.4% of patients in the placebo group (adjusted difference, 36.0% [95% CI, 19.4%-52.6%]; adjusted relative risk, 2.3 [95% CI, 1.5-3.6]; P < .001). Of 11 reported secondary end points at 24 weeks, 7 showed significant differences favoring tocilizumab, including mean CRP PMR-AS score (7.5 [95% CI, 5.4-9.6] vs 14.9 [95% CI, 11.4-18.4]; adjusted difference, -7.5 [95% CI, -11.2 to -3.8]; P < .001) and the percentage of patients no longer receiving prednisone (49.0% vs 19.6%; adjusted difference, 29.3% [95% CI, 18.9%-39.7%]; adjusted relative risk, 2.5 [95% CI, 1.8-3.5]; P < .001). The most frequent adverse events were infections, experienced by 23 patients (46.9%) in the tocilizumab group and 20 (39.2%) in the placebo group.

CONCLUSIONS AND RELEVANCE

Among patients with active polymyalgia rheumatica despite prednisone therapy, tocilizumab, compared with placebo, resulted in a significantly greater percentage of patients with a CRP PMR-AS less than 10 with reduced prednisone requirements at week 24. Further research is needed to confirm efficacy and to determine the balance of potential benefits and harms.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02908217.

Measurement properties of the PolyMyalgia Rheumatica Activity Score (PMR-AS): a systematic literature review

Objective

To perform a COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) based Systematic Literature Review of measurement properties of the Polymyalgia Rheumatica Activity Score (PMR-AS).

Methods

Pubmed, EMBASE, and CINAHL were broadly searched. English full text articles, with (quantitative) data on at least 5 PMR patients using the PMR-AS were selected. Seven hypotheses for construct validity and three for responsiveness, concerning associations with erythrocyte sedimentation rate, physical function, quality of life, clinical disease states, ultrasound, and treatment response, were formulated. Articles usable to assess - COSMIN based - structural validity, internal consistency, reliability, measurement error, or hypotheses on construct validity or responsiveness were selected and assessed based on COSMIN criteria.

Results

From the 26 articles using the PMR-AS we were able to use 12 articles. Structural validity, internal consistency, construct validity, and responsiveness were assessed in one, two, eight, and three articles respectively. Insufficient evidence was found to confirm structural validity and internal consistency. No data was found on reliability or measurement error. Although 60% and 67% of hypotheses tested for construct validity and responsiveness were confirmed respectively, there was insufficient evidence to meet criteria for good measurement properties.

Conclusion

Whilst there is some promising evidence for construct validity and responsiveness of the PMR-AS, it is lacking for other properties and overall falls short of criteria for good measurement properties. Therefore, further research is needed to assess its role in clinical research and care.

"The added value of 18f-FDG PET/CT in the assessment of onset and steroid resistant polimyalgia rheumatica"

PMR is a common inflammatory rheumatic disease. Although its clinical characteristics are fully recognized, no specific test for its diagnosis has been established to date. Several studies have described a wide variety of diseases that present with polymyalgic symptoms. A 18FDG-PET/CT scan could help to deal with these differential diagnoses. The goal of our study is to describe the findings of the 18FDG-PET/CT scan in a cohort of PMR patients and to detail how the 18FDG-PET/CT scan improves accuracy when diagnosing other underlying conditions. This cross-sectional study enrolled patients with a diagnosis of PMR who underwent to a 18FDG-PET/CT scan to rule out other diagnosis. The 18FDG-PET/CT scan was performed either following clinical criteria at the onset of clinical symptoms or when the patient became PMR steroid resistant. Patients' demographic, clinical and analytical data at the moment of the 18FDG-PET/CT scan were recorded. The final diagnosis was confirmed according to clinical judgement. A total of 103 patients with PMR were included. In 49.51% of patients, the 18FDG-PET/CT scan was ordered to study resistance to steroid therapy. The final diagnoses of patients were PMR in 70.9% patients, large vessel vasculitis in 15.5%, neoplasms 4.8% and another diagnosis in the rest. The 18FDG-PET/CT scan is a very useful technique for the study of Polymyalgia Rheumatica, not only to help in the diagnostic process, but also due to its role in the identification of a variety of PMR-like patrons.

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.

Comparison and validation of FDG-PET/CT scores for polymyalgia rheumatica

Objectives

To compare and validate the diagnostic accuracy of fluorodeoxyglucose (FDG)-PET/CT scores for PMR; and to explore their association with clinical factors.

Methods

This retrospective study included 39 consecutive patients diagnosed with PMR and 19 PMR comparators. The final clinical diagnosis was established after 6 months follow-up. Patients underwent FDG-PET/CT prior to glucocorticoid treatment. Visual grading of FDG uptake was performed at 30 anatomic sites. Three FDG-PET/CT scores (the Leuven Score, two Besançon Scores) and two algorithms (the Saint-Etienne and Heidelberg Algorithms) were investigated. Receiver operating characteristic (ROC) analysis with area under the curve (AUC) was performed. Diagnostic accuracy was assessed at predefined cut-off points.

Results

All three FDG-PET/CT scores showed high diagnostic accuracy for a clinical diagnosis of PMR in the ROC analysis (AUC 0.889–0.914). The Leuven Score provided a sensitivity of 89.7% and specificity of 84.2% at its predefined cut-off point. A simplified Leuven Score showed similar diagnostic accuracy to that of the original score. The Besançon Scores showed limited specificity at their predefined cut-off points (i.e. 47.4% and 63.2%), while ROC analysis suggested that substantially higher cut-off points are needed for these scores. The Heidelberg and Saint-Etienne Algorithms demonstrated high sensitivity, but lower specificity (i.e. 78.9% and 42.1%, respectively) for PMR. Female sex and presence of large-vessel vasculitis were associated with lower FDG-PET/CT scores in patients with PMR.

Conclusion

The Leuven Score showed the highest diagnostic utility for PMR. A modified, concise version of the Leuven Score provided similar diagnostic accuracy to that of the original score.

New insights into the role of imaging in polymyalgia rheumatica

PMR is an inflammatory rheumatic disease of elderly people characterized by pain and stiffness in the neck, shoulder and pelvic girdles. No specific diagnostic confirmatory tests exist and clinical symptoms, as well as increased acute phase reactants, are unspecific. The diagnostic value of imaging including ultrasound, MRI and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) with/without CT for PMR is increasingly studied. These techniques, particularly FDG-PET/CT, may help to detect underlying GCA in PMR patients with an incomplete response to glucocorticoids and/or recurrent relapses. Recent imaging studies provide novel insights into the anatomical basis of inflammation in PMR, particularly at hip and spine, which may help to distinguish this disease from other mimicking conditions. In this review, we discuss novel insights into the pathoanatomy of PMR, compare the diagnostic values of different imaging techniques and summarize current data on the role of imaging for monitoring and outcome prediction.

Diagnostic value of [18F]FDG-PET/CT in polymyalgia rheumatica: a systematic review and meta-analysis

Purpose

Polymyalgia rheumatica (PMR) can be difficult to diagnose. Whole-body [18F]FDG-PET/CT allows for a comprehensive evaluation of all relevant articular and extra-articular structures affected by PMR. We aimed to summarize current evidence on the diagnostic value of [18F]FDG-PET/CT for a diagnosis of PMR.

Methods

PubMed/MEDLINE and the Cochrane Library database were searched from inception through May 31, 2020. Studies containing patients with PMR who underwent [18F]FDG-PET/CT were included. Screening and full-text review were performed by 3 investigators and data extraction by 2 investigators. Risk of bias was examined with the QUADAS-2 tool. Diagnostic test meta-analysis was performed with a bivariate model.

Results

Twenty studies were included in the systematic review, of which 9 studies (n = 636 patients) were eligible for meta-analysis. [18F]FDG positivity at the following sites was associated with a diagnosis of PMR: interspinous bursae (positive likelihood ratio (LR+) 4.00; 95% CI 1.84–8.71), hips (LR+ 2.91; 95% CI 2.09–4.05), ischial tuberosities (LR+ 2.86; 95% CI 1.91–4.28), shoulders (LR+ 2.57; 95% CI 1.24–5.32) and sternoclavicular joints (LR+ 2.31; 95% CI 1.33–4.02). Negative likelihood ratios (LR−) for these sites, as well as the greater trochanters, were all less than 0.50. Composite [18F]FDG-PET/CT scores, as reported in 3 studies, provided a pooled LR+ of 3.91 (95% CI 2.42–6.32) and LR− of 0.19 (95% CI 0.10–0.36). Moderate to high heterogeneity was observed across the studies, mainly due to differences in patient selection, scanning procedures and/or interpretation criteria.

Conclusion

Significant [18F]FDG uptake at a combination of anatomic sites is informative for a diagnosis of PMR. [18F]FDG-PET/CT might be an important diagnostic tool in patients with suspected PMR. This study also highlights the need for adherence to published procedural recommendations and standardized interpretation criteria for the use of [18F]FDG-PET/CT in PMR.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-020-05162-6.

Utility of 18F-Fluorodeoxyglucose Positron Emission Tomography in Inflammatory Rheumatism, Particularly Polymyalgia Rheumatica: A Retrospective Study of 222 PET/CT

Purpose: The objective of this study was to evaluate periarticular FDG uptake scores from ¹⁸F-FDG-PET/CT to identify polymyalgia rheumatica (PMR) within a population presenting rheumatic diseases.

Methods: A French retrospective study from 2011 to 2015 was conducted. Patients who underwent ¹⁸F-FDG-PET/CT for diagnosis or follow-up of a rheumatism or an unexplained biological inflammatory syndrome were included. Clinical data and final diagnosis were reviewed. Seventeen periarticular sites were sorted by a visual reading enabling us to calculate two scores: mean FDG visual uptake score, number of sites with significant uptake same as that or higher than liver uptake intensity and by a semi-quantitative analysis using mean maximum standardized uptake value (SUVmax). Optimal cutoffs of visual score and SUVmax to diagnose PMR were determined using receiver operating characteristics curves.

Results: Among 222 ¹⁸F-FDG PET/CT selected for 215 patients, 161 ¹⁸F-FDG PET/CT were performed in patients who presented inflammatory rheumatism as a final diagnosis (of whom 57 PMR). The presence of at least three sites with significant uptake identified PMR with a sensitivity of 86% and a specificity of 85.5% (AUC 0.872, 95% CI [0.81–0.93]). The mean FDG visual score cutoff to diagnose a PMR was 0.765 with a sensitivity of 82.5% and a specificity of 75.8% (AUC 0.854; 95% CI [0.80–0.91]). The mean SUVmax cutoff to diagnose PMR was 2.168 with a sensitivity of 77.2% and a specificity of 77.6% (AUC 0.842; 95% CI [0.79–0.89]).

Conclusions: This study suggests that ¹⁸F-FDG PET/CT had good performances to identify PMR within a population presenting rheumatic diseases.

Diagnosis and Monitoring of Osteoporosis with Total-Body 18F-Sodium Fluoride-PET/CT

In recent years, ¹⁸F-Sodium Fluoride (NaF)-PET/CT has seen its role in the detection and management of osteoporosis increase. This article reviews the extent of this application in the literature, its efficacy compared with other comparable imaging tools, and how total-body PET/CT combined with global disease assessment can revolutionize measurement of total osteoporotic disease activity. NaF-PET/CT eventually can be the modality of choice for metabolic bone disorders, especially with these advances in technology and computation.

[Positron emission tomography/computed tomography in rheumatology]

Combined positron emission tomography/computed tomography (PET/CT) is a whole-body imaging procedure, which enables sensitive detection of inflammatory changes. It may be used to simultaneously obtain both precise anatomical and molecular information in order to comprehensively characterize diseases. The glucose analogue ¹⁸F-fluorodeoxyglucose (FDG) represents a universally applicable radiotracer for imaging of inflammatory processes. Its accumulation in tissues can be semiquantitatively characterized by use of standardized uptake values (SUV). In principle, a broad spectrum of infectious and non-infectious inflammatory and malignant diseases can be imaged. ¹⁸F-FDG PET/CT has become a valuable modality and is increasingly being used for evaluation of large vessel vasculitis and for evaluation of elevated systemic inflammatory markers without known cause. Beside the radiotracer ¹⁸F-FDG, other radiopharmaceuticals enable a non-invasive analysis of additional parameters of inflammatory disorders, such as other metabolic pathways or the expression of surface receptors.

Clinical Nononcologic Applications of PET/CT and PET/MRI in Musculoskeletal, Orthopedic, and Rheumatologic Imaging

OBJECTIVE

With improvements in PET/CT and PET/MRI over the last decade, as well as increased understanding of the pathophysiology of musculoskeletal diseases, there is an emerging potential for PET as a primary or complementary modality in the management of rheumatologic and orthopedic conditions.

CONCLUSION

We discuss the role of PET/CT and PET/MRI in nononcologic musculoskeletal disorders, including inflammatory and infectious conditions and postoperative complications. There is great potential for an increased role for PET to serve as a primary or complementary modality in the management of orthopedic and rheumatologic disorders.

Localized Myofascial Inflammation Revealed by Magnetic Resonance Imaging in Recent-onset Polymyalgia Rheumatica and Effect of Tocilizumab Therapy

OBJECTIVE

To assess the prevalence of myofascial inflammatory lesions visible by magnetic resonance imaging (MRI) and their changes after tocilizumab (TCZ) therapy in active polymyalgia rheumatica (PMR).

METHODS

We conducted a posthoc analysis of data from the TENOR study of TCZ monotherapy in PMR. The 18 patients each received TCZ injections at weeks 0, 4, and 8. The shoulder and pelvic girdles were assessed at baseline then at weeks 2 and 12 using T1- and T2- short-tau inversion recovery-weighted MRI. Radiologists blinded to patient data assessed each muscle group for localized myofascial inflammation on baseline, Week 2, and Week 12 MRI. Reproducibility was estimated by having 2 radiologists assess the Week 2 MRI of 13 patients, then computing the κ coefficient.

RESULTS

For myofascial lesion detection, intraobserver reproducibility was almost perfect (κ = 0.890) and interobserver reproducibility was substantial (κ = 0.758). At baseline, all patients had at least 1 inflammatory myofascial lesion; sites involved were the shoulder in 10 (71.4%) patients, hip in 13 (86.7%), ischial tuberosity in 9 (60.0%), and pubic symphysis in 12 (80.0%). Sites involved at Week 12 were the shoulder in 8 patients (53.3%), hip in 5 (33.3%), ischial tuberosity in 1, and pubic symphysis in 3 (20.0%). At Week 12, of 103 muscle groups studied in all, 43 (41.7%) had no inflammatory lesions, compared to 33 at baseline (p = 0.002); improvements were noted in 66 (64.1%) muscle groups, worsening in 2 (1.9%), no change in 35 (34.0%; p = 0.034).

CONCLUSION

Localized myofascial inflammatory lesions are common in recent-onset PMR and improve during TCZ therapy. Clinicaltrials.gov (NCT01713842).

FDG-PET/CT(A) imaging in large vessel vasculitis and polymyalgia rheumatica: joint procedural recommendation of the EANM, SNMMI, and the PET Interest Group (PIG), and endorsed by the ASNC

Large vessel vasculitis (LVV) is defined as a disease mainly affecting the large arteries, with two major variants, Takayasu arteritis (TA) and giant cell arteritis (GCA). GCA often coexists with polymyalgia rheumatica (PMR) in the same patient, since both belong to the same disease spectrum. FDG-PET/CT is a functional imaging technique which is an established tool in oncology, and has also demonstrated a role in the field of inflammatory diseases. Functional FDG-PET combined with anatomical CT angiography, FDG-PET/CT(A), may be of synergistic value for optimal diagnosis, monitoring of disease activity, and evaluating damage progression in LVV. There are currently no guidelines regarding PET imaging acquisition for LVV and PMR, even though standardization is of the utmost importance in order to facilitate clinical studies and for daily clinical practice. This work constitutes a joint procedural recommendation on FDG-PET/CT(A) imaging in large vessel vasculitis (LVV) and PMR from the Cardiovascular and Inflammation & Infection Committees of the European Association of Nuclear Medicine (EANM), the Cardiovascular Council of the Society of Nuclear Medicine and Molecular Imaging (SNMMI), and the PET Interest Group (PIG), and endorsed by the American Society of Nuclear Cardiology (ASNC). The aim of this joint paper is to provide recommendations and statements, based on the available evidence in the literature and consensus of experts in the field, for patient preparation, and FDG-PET/CT(A) acquisition and interpretation for the diagnosis and follow-up of patients with suspected or diagnosed LVV and/or PMR. This position paper aims to set an internationally accepted standard for FDG-PET/CT(A) imaging and reporting of LVV and PMR.

Ultrasonography and magnetic resonance imaging changes in patients with polymyalgia rheumatica treated by tocilizumab

BACKGROUND

This study assessed inflammatory changes using ultrasound (US) and magnetic resonance imaging (MRI) in patients taking tocilizumab for polymyalgia rheumatica (PMR).

METHODS

Eighteen patients were included in the prospective open-label TENOR study and received three tocilizumab infusions, without corticosteroids. B-mode and power Doppler US and MRI (T1 and T2-short time inversion recuperation weighted sequences) of the hips and shoulders were performed at weeks 0, 2, and 12. Subacromial, trochanteric, and iliopsoas bursitis and intraarticular glenohumeral and coxofemoral effusions/synovitis were scored from 0 to 3. Changes over time and US-MRI correlations were evaluated.

RESULTS

At baseline, the proportions of shoulders and hips with bursitis were 93 and 100% by MRI and 61 and 13% by US; and the corresponding proportions for intraarticular effusions/synovitis were 100 and 100% by MRI and 57 and 53% by US. Imaging findings did not improve during the first two treatment weeks. From baseline to week 12, bursitis improved significantly at all four joints by MRI (P = 0.005) and US (P = 0.029) and intraarticular effusions/synovitis by US only (P = 0.001). The proportion of abnormalities that improved by week 12 was 42% by MRI and 37% by US. MRI detected bursitis in a larger proportion of hips (73% versus 13%) and US in a larger proportion of shoulders (57% versus 28%), whereas no difference was found for intraarticular effusions/synovitis. At baseline, agreement between US and MRI findings was poor.

CONCLUSIONS

US and MRI showed significant improvements in inflammatory lesions during tocilizumab treatment of PMR.

Multiple values of 18F-FDG PET/CT in idiopathic inflammatory myopathy

This study aimed to investigate the multiple values of ¹⁸F-FDG PET/CT in detecting malignant tumors, evaluating myopathy, and determining interstitial lung disease in patients with idiopathic inflammatory myopathy (IIM). We retrospectively analyzed the data of 38 patients who were examined by ¹⁸F-FDG PET/CT and eventually diagnosed as IIM. We also collected the data of another 22 cases with negative PET/CT as the control. Pulmonary HRCT images were acquired simultaneously with regular ¹⁸F-FDG PET/CT imaging for each patient. Image analysis included the presence of malignant lesions, muscular FDG uptake, and interstitial lung disease and its imaging features. IIM was classified into polymyositis (PM), classic dermatomyositis (CDM), and clinical amyopathic dermatomyositis (CADM). All suspected malignant lesions were confirmed by histopathological examination. Interstitial lung disease was diagnosed by HRCT. Rapidly progressive interstitial lung disease (RP-ILD) was determined according to clinical follow-ups. The significance of ¹⁸F-FDG PET/CT in the detection of malignancy, observation of activity of myopathy, and determination of interstitial lung disease in IIM patients was explored based on the final clinical diagnosis. In the 38 patients with IIM, 3 cases were classified as PM, 18 as CDM, and 17 as CADM. PET/CT correctly detected 7 cases (18.4%) of malignant tumors, and all of which were found in CDM and PM patients. The muscular FDG uptake in IIM patients was higher than the control population, and it was higher in patients with myopathy (including PM and CDM) than in patients with CADM. The muscular FDG uptake in IIM patients was correlated with elevated serum creatine kinase level (r = 0.332, P = 0.042) and impaired muscle strength (r = -0.605, P < 0.001). Interstitial lung disease was detected by HRCT in 30 patients (78.9%), and 7 of them were eventually confirmed as RP-ILD, according to the clinical outcome. The FDG uptake in lung lesions of RP-ILD patients was higher than those with chronic interstitial lung diseases, even though no significant difference was found between the CT features of RP-ILD and chronic interstitial lung disease. When SUV_max ≥ 2.4 was employed as the threshold for RP-ILD prediction, the diagnostic efficiency was yield with a sensitivity of 100.0% (7/7), specificity of 87.0% (20/23), and accuracy of 90.0% (27/30), respectively. For IIM patients, ¹⁸F-FDG PET/CT has multiple values in identifying malignancies, observing the status of inflammatory myopathy, detecting interstitial lung disease, and predicting the occurrence of RP-ILD. Therefore, it is recommended to use PET/CT in the clinical course of diagnosis and management of IIM.

18F-FDG PET/CT in polymyalgia rheumatica-a pictorial review

Polymyalgia rheumatica (PMR) is one of the inflammatory rheumatic diseases that can potentially be detected by positron emission tomography/CT. High fluorine-18 fludeoxyglucose (¹⁸F-FDG) accumulation around the shoulders, sternoclavicular and hip joints are the most common pre-treatment features of patients with PMR. Another common sign is increased ¹⁸F-FDG uptake in extra-articular regions between columnal spinous processes, near ischial tuberosities and in the praepubic area. Some patients also present with high ¹⁸F-FDG uptake in main arteries, corresponding to the characteristics of giant cell arteritis. It is possible to observe a decrease or even a disappearance of ¹⁸F-FDG uptake after effective therapy, an event which may be useful for the monitoring of treatment as well as for detection of PMR relapse.

F-18 FDG PET/CT imaging of cardiac and vascular inflammation and infection

INTRODUCTION

Inflammation forms an important core of the aetiopathogenic process involved in many diseases affecting the heart and the blood vessels. These diseases include infections as well as inflammatory non-infectious cardiovascular conditions. The common feature of this is invasion of the heart or blood vessel by inflammatory cells. F-18 2-fluoro 2-deoxy-D glucose (FDG) is an analogue of glucose and like glucose it is taken up by activated inflammatory cells that accumulate at the site of infection. This has formed the basis of the use of F-18 FDG PET/CT in the non-invasive evaluation of human inflammatory diseases.

SOURCES OF DATA

This review is based on the published academic articles as well as our clinical experience.

AREAS OF AGREEMENT

F-18 FDG PET/CT is a useful imaging modality in the evaluation of cardiovascular inflammatory disorders. Accumulation and distribution of F-18 FDG at the site of inflammation/infection corresponds to severity of the inflammation/infection and extent of involvement.

AREAS OF CONTROVERSY

Most studies evaluating utility of F-18 FDG PET/CT in imaging cardiovascular inflammation are small observational studies hence are potentially prone to bias.

GROWING POINTS

Being a hybrid metabolic and morphologic imaging technique, F-18 FDG PET/CT offers combined advantage of complementary anatomic and metabolic information in disease process. This makes it a useful modality in the diagnosis, determination of extent of disease, prognostication as well as treatment monitoring.

AREAS TIMELY FOR DEVELOPING RESEARCH

Larger prospective studies are needed to validate the superiority of F-18 FDG PET/CT imaging over conventional anatomic imaging modalities.