The lungs were on fire: a pilot study of 18F-FDG PET/CT in idiopathic-inflammatory-myopathy-related interstitial lung disease

Exploring the Potential Value of [68Ga]Ga-FAPI-46 PET/CT for Molecular Assessment of Fibroblast Activation in Interstitial Lung Disease: A Single-Center Pilot Study

BACKGROUND

The aim of the study was to evaluate the association of high-resolution computed tomography (HRCT) findings with pulmonary fibrotic activity in the corresponding regions using [68Ga]Ga-fibroblast activation fibroblast inhibitor (FAPI) PET/CT in patients with interstitial lung disease (ILD). Additionally, the potential of [68Ga]Ga-FAPI-46 PET/CT for evaluating the active fibrosis process and 99mTc-MIBI scintigraphy for assessing the inflammatory process in ILD patients was also assessed.

METHODS

In this pilot study, 20 ILD patients underwent [68Ga]Ga-FAPI-46 PET/CT and 99mTc-MIBI SPECT/CT. Additionally, 10 patients without lung or thoracic involvement who were undergoing [68Ga]Ga-FAPI PET/CT for cancer detection were enrolled in the control group. The images were evaluated both visually and semiquantitatively and also compared with HRCT and pulmonary function tests. Multiple quantitative parameters were derived from the lung segments in the PET scan, including SUVmax, SUVmean, maximum target-to-liver ratio, mean target-to-liver ratio (TLRmean), and total lesion FAPI expression for the entire lung, as well as its lobes and zones. Additionally, the maximum Hounsfield unit (HU) and mean HU in HRCT were calculated for the whole lung as well as its lobes and zones. Furthermore, an HRCT fibrosis score (HFS) was defined according to the HRCT findings.

RESULTS

Twenty ILD patients with a mean age of 58.70 (SD, 11.09) years were enrolled. Additionally, 10 control patients were enrolled with a mean age of 57.70 (SD, 15.19) years. Based on visual assessment, the FAPI scan was positive in 12 (60%) patients. Similarly, the MIBI scan was positive in 12 (60%) patients. In the 20 ILD cases, both scans were positive in 6 cases, and both were negative in 2 cases. Six cases showed FAPI-negative and MIBI-positive results, whereas another 6 cases showed FAPI-positive and MIBI-negative results. Comparing the control and ILD patients, there was a significant difference in SUVmax, SUVmean, total lesion FAPI expression, TLRmean, maximum HU, and mean HU (P < 0.05). When comparing HFS with PET-derived parameters in zones, a significant positive correlation was found between HFS and SUVmean, SUVmax, maximum target-to-liver ratio, and TLRmean (P < 0.05). Additionally, a significant difference was noted between FAPI results and HFS (P = 0.003). An ancillary finding, 9 of 20 (45%) ILD patients showed intense FAPI uptakes in gallbladder, whereas none of the 10 in the control group showed such uptake.

CONCLUSION

The present study may suggest that combining [68Ga]Ga-FAPI PET/CT and 99mTc-MIBI SPECT/CT yields an additive effect for evaluating ILD-related fibrosis and inflammatory processes over using either modality alone. Furthermore, it appears that [68Ga]Ga-FAPI PET/CT has the potential to ascertain levels of fibrotic activity from population of resident fibroblasts, active fibroblasts, and scar maturation among ILD patients based on their HRCT patterns.

An externally validated clinical-laboratory nomogram for myocardial involvement in adult idiopathic-inflammatory-myopathy patients

OBJECTIVES

This study aimed at identifying clinical and laboratory risk factors for myocardial involvement (MI) in idiopathic inflammatory myopathies (IIMs) patients as well as constructing a risk-predicted nomogram for prediction and early identification of MI.

METHODS

An IIMs cohort in southeastern China was constructed, including 504 adult IIMs patients who met the inclusion and exclusion criteria, and were hospitalized at four divisions of the First Affiliated Hospital, Zhejiang University School of Medicine from January 1st 2018 to April 30st 2022. After dividing patients into the training cohort and the validation cohort, risk factors for MI were identified through least absolute shrinkage and selection operator regression and multivariate logistic regression. A risk-predicted nomogram was established and validated internally and externally for discrimination, calibration and practicability.

RESULTS

In this cohort, 17.7% of patients developed MI and the survival was significantly inferior to that of IIMs patients without MI (P < 0.001). In the training cohort, age > 55 years old (P < 0.001), disease activity > 10 points (P < 0.001), interleukin-17A (IL-17A) > 7.5 pg/ml (P < 0.001), lactic dehydrogenase (LDH) > 425 U/L (P < 0.001), anti-mitochondrial antibodies (AMAs, P = 0.017), and anti-MDA5 antibody (P = 0.037) were significantly correlated with development of MI. A nomogram was established by including the above values to predict MI and was found efficient in discrimination, calibration, and practicability through internal and external validation.

CONCLUSION

This study developed and validated a nomogram model to predict the risk of MI in adult IIMs patients, which can benefit the prediction and early identification of MI as well as timely intervention in these patients.

Lung functional imaging

Pulmonary functional imaging modalities such as computed tomography, magnetic resonance imaging and nuclear imaging can quantitatively assess regional lung functional parameters and their distributions. These include ventilation, perfusion, gas exchange at the microvascular level and biomechanical properties, among other variables. This review describes the rationale, strengths and limitations of the various imaging modalities employed for lung functional imaging. It also aims to explain some of the most commonly measured parameters of regional lung function. A brief review of evidence on the role and utility of lung functional imaging in early diagnosis, accurate lung functional characterisation, disease phenotyping and advancing the understanding of disease mechanisms in major respiratory disorders is provided.

[18F]FDG-PET/CT in Idiopathic Inflammatory Myopathies: Retrospective Data from a Belgian Cohort

[¹⁸F]FDG-PET/CT is a useful tool for diagnosis and cancer detection in idiopathic inflammatory myopathies (IIMs), especially polymyositis (PM) and dermatomyositis (DM). Data deriving from Europe are lacking. We describe [¹⁸F]FDG-PET/CT results in a Belgian cohort with IIMs, focusing on patients with PM and DM. All of the cases of IIMs admitted between December 2010 and January 2023 to the Cliniques Universitaires Saint-Luc (Belgium) were retrospectively reviewed. In total, 44 patients were identified with suspected IIMs; among them, 29 were retained for final analysis. The mean age of the retained patients was 48.7 years; 19 patients were female (65.5%). Twenty-two patients had DM and seven had PM. The mean serum creatinine kinase (CK) and the mean CRP levels were 3125 UI/L and 30.3 mg/L, respectively. [¹⁸F]FDG-PET/CT imaging was performed for 27 patients, detecting interstitial lung diseases (ILDs) in 7 patients (25.9%), cancer in 3 patients (11.1%), and abnormal muscle FDG uptake compatible with myositis in 13 patients (48.1%). All of the patients who were detected to have ILDs via PET/CT imaging were confirmed using a low-dose lung CT scan. Among the patients who were detected to have abnormal muscle FDG uptake via PET/CT scans (13/28), the EMG was positive in 12 patients (p = 0.004), while the MRI was positive in 8 patients (p = 0.02). We further observed that there was a significantly higher level of CK in the group with abnormal muscle FDG uptake (p = 0.008). Our study showed that PET/CT is useful for detecting cancer and ILDs. We showed that the detection of abnormal muscle uptake via PET/CT was in accordance with EMG and MRI results, as well as with the mean CK value, and that the presence of dyspnea was significantly associated with the presence of ILDs detected via PET/CT imaging (p = 0.002).

The potential role of 18 F-FDG PET/CT in dermatomyositis with cardiac involvement: A case report

BACKGROUND

Dermatomyositis (DM) is a chronic inflammatory muscle disease. Cardiac involvement is reported to be a main cause of death in DM but typically remains subclinical. Delayed or missed diagnosis renders more severe prognosis in DM patients.

CASE SUMMARY

A 69-year-old man with a 6-month history of shortness of breath, cough and characteristic cutaneous lesions was diagnosed with DM complicated with interstitial lung disease on his first admission. Within 47 days, the patient developed progressive heart failure with dyspnea. The levels of B-type natriuretic peptide and Troponin I drastically increased and the cardiac function prominently decreased. According to the result of cardiac magnetic resonance, he was finally diagnosed with DM combined with cardiac involvement. Interestingly, the abnormal cardiac metabolism on ¹⁸ F-fluorodeoxyglucose positron emission tomography / computed tomography FDG PET/CT had been found before the cardiac involvement was clinically identified.

CONCLUSIONS

¹⁸ F-FDG PET/CT may play a potential role in early recognition of cardiac involvement in patients with DM, although more data is still needed.

Novel tracers for molecular imaging of interstitial lung disease: A state of the art review

Interstitial lung disease is an overarching term for a wide range of disorders characterized by inflammation and/or fibrosis in the lungs. Most prevalent forms, among others, include idiopathic pulmonary fibrosis (IPF) and connective tissue disease associated interstitial lung disease (CTD-ILD). Currently, only disease modifying treatment options are available for IPF and progressive fibrotic CTD-ILD, leading to reduction or stabilization in the rate of lung function decline at best. Management of these patients would greatly advance if we identify new strategies to improve (1) early detection of ILD, (2) predicting ILD progression, (3) predicting response to therapy and (4) understanding pathophysiology. Over the last years, positron emission tomography (PET) and single photon emission computed tomography (SPECT) have emerged as promising molecular imaging techniques to improve ILD management. Both are non-invasive diagnostic tools to assess molecular characteristics of an individual patient with the potential to apply personalized treatment. In this review, we encompass the currently available pre-clinical and clinical studies on molecular imaging with PET and SPECT in IPF and CTD-ILD. We provide recommendations for potential future clinical applications of these tracers and directions for future research.

Predictors of progression in idiopathic inflammatory myopathies with interstitial lung disease

The idiopathic inflammatory myopathies (IIMs) are a group of connective tissue diseases that afect multiple organ systems, including the lungs. Interstitial lung disease (ILD) is the most common and heterogeneous complication of IIMs, with its degree ranging from mild to fatal. Thus, it is critical to identify clinical features and validated biomarkers for predicting disease progression and prognosis, which could be beneficial for therapy adjustment. In this review, we discuss predictors for rapid progression of IIM-ILD and propose guidance for disease monitoring and implications of therapy. Systematic screening of myositis-specific antibodies, measuring serum biomarker levels, pulmonary function tests, and chest high-resolution computer tomography will be beneficial for the evaluation of disease progression and prognosis.

Evaluation of Interstitial Lung Disease in Idiopathic Inflammatory Myopathies Through Semiquantitative and Quantitative Analysis of Lung Computed Tomography

PURPOSE

To perform a semiquantitative and quantitative analysis of interstitial lung disease (ILD), through computed tomography (CT), in different serological subgroups of idiopathic inflammatory myopathies (IIM) patients, to find radiologic and clinical differences of disease related to serology.

MATERIALS AND METHODS

This was a prospective study, which included 98 IIM patients, divided into serological subgroups: anti-aminoacyl-transfer-RNA-synthetases (anti-ARS) positive and myositis-specific autoantibodies (MSA) negative.For each baseline CT the total semiquantitative score of Warrick (WS) and the automated software (Computer-Aided Lung Informatics for Pathology Evaluation and Rating) quantitative scores interstitial lung disease % (ILD%) and vascular-related structure % (VRS%) were calculated. Pulmonary function tests included total lung capacity % (TLC%), forced vital capacity % (FVC%), and diffusing capacity of the lung for carbon monoxide % (DLCO%).

RESULTS

Inverse correlations ( P <0.001) between the radiologic scores and the functional scores DLCO% and TLC% were found, the most relevant being between ILD% and DLCO% (ρ=-0.590), VRS% and DLCO% (ρ=-0.549), and WS and DLCO% (ρ=-0.471).Positive correlations between ILD% and VRS% (ρ=0.916; P <0.001), WS and ILD% (ρ=0.663; ρ<0.001), and WS and VRS% (ρ=0.637; P <0.001) were obtained.Statistically significant higher values of WS, ILD%, and VRS% were found in the anti-ARS group (WS=15; ILD%=11; VRS%=3.5) compared with the MSA negative one (WS=2.5; ILD%=0.84; VRS%=2.2).The nonspecific interstitial pneumonia pattern was dominant. No statistically significant differences emerged at pulmonary function tests.

CONCLUSIONS

In this study, ILD in anti-ARS-positive and MSA-negative groups was defined through semiquantitative and quantitative analysis of lung CT. The inverse correlations between the radiologic scores and TLC% and DLCO% ( P <0.001) confirm the role of lung CT in the evaluation of ILD in IIM.

18F-FDG PET/CT and HRCT: a combined tool for risk stratification in idiopathic inflammatory myopathy-associated interstitial lung disease

OBJECTIVES

Rapidly progressive interstitial lung disease (RP-ILD) is a life-threatening form of idiopathic inflammatory myopathy (IIM)-associated interstitial lung disease (ILD). We aimed to assess the combination of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) and high-resolution computed tomography (HRCT) for the quantification of IIM-ILD activity and risk stratification for RP-ILD.

METHOD

Patients with IIM and undergoing ¹⁸F-FDG PET/CT were included in this retrospective study. Pulmonary FDG uptake was assessed using the maximum standardized uptake value (SUV_lung) and visual score (PET score). HRCT was evaluated using visual analysis (HRCT score). Multivariable logistic regression was used to identify risk factors for RP-ILD.

RESULTS

Seventy-three patients with IIM (17 with RP-ILD, 38 with non-RP-ILD, and 18 without ILD) were included. SUV_lung, PET score, and HRCT score were significantly higher in RP-ILD than in non-RP-ILD. Strong positive correlations were observed between SUV_lung, PET score, and the HRCT parameters. The area under the curve (AUC) of the PET score to differentiate between RP-ILD and non-RP-ILD (AUC = 0.860) was higher than that of the SUV_lung (AUC = 0.802) and HRCT scores (AUC = 0.806). We developed a risk score based on the number of positive risk factors (PET score > 18, HRCT score > 140, and positive anti-melanoma differentiation-associated gene 5 (MDA5) antibody) to differentiate between RP-ILD and non-RP-ILD (AUC = 0.955). Patients with higher risk scores had significantly worse prognoses.

CONCLUSIONS

¹⁸F-FDG PET/CT is useful for assessing disease activity in patients with IIM-ILD. The combination of PET score, HRCT score, and anti-MDA5 antibody can be used to identify patients at increased risk of RP-ILD and with poor prognoses.

Muscle imaging in myositis: MRI, US, and PET

Imaging is an important tool in the evaluation of idiopathic inflammatory myopathies. It plays a role in diagnosis, assessment of disease activity and follow-up, and as a non-invasive biomarker. Among the different modalities, nuclear magnetic resonance imaging (MRI), ultrasound (US), and positron emission tomography (PET) may have the most clinical utility in myositis. MRI is currently the best modality to evaluate skeletal muscle and provides excellent characterization of muscle edema and fat replacement through the use of T1-weighted and T2-weighted fat suppressed/STIR sequences. Although MRI can be read qualitatively for the presence of abnormalities, a more quantitative approach using Dixon sequences and the generation of water T2 parametric maps would be preferable for follow-up. Newer protocols such as diffusion-weighted imaging, functional imaging measures, and spectroscopy may be of interest to provide further insights into myositis. Despite the advantages of MRI, image acquisition is relatively time-consuming, expensive, and not accessible to all patients. The use of US to evaluate skeletal muscle in myositis is gaining interest, especially in chronic disease, where fat replacement and fibrosis are detected readily by this modality. Although easily deployed at the bedside, it is heavily dependent on operator experience to recognize disease states. Further, systematic characterization of muscle edema by US is still needed. PET provides valuable information on muscle function at a cellular level. Fluorodeoxyglucose (FDG-PET) has been the most common application in myositis to detect pathologic uptake indicative of inflammation. The use of neurodegenerative markers is now also being utilized for inclusion body myositis. These different modalities may prove to be complementary methods for myositis evaluation.

The Role of Quantitative and Semi-quantitative [18F]FDG-PET/CT Indices for Evaluating Disease Activity and Management of Patients With Dermatomyositis and Polymyositis

Idiopathic inflammatory myopathies (IIM) are considered systemic diseases involving different organs and some subtypes are associated with increased cancer risk. In this review, we provide a comprehensive summary of the current use and potential applications of (semi-)quantitative [18F]FDG-PET/CT indices in patients with IIM focusing on dermatomyositis and polymyositis. Visual interpretation and (semi-)quantitative [18F]FDG-PET indices have a good overall performance to detect muscle activity but objective, robust and standardized interpretation criteria are currently lacking. [18F]FDG-PET/CT is a suitable modality to screen for malignancy in patients with myositis and may be a promising tool to detect inflammatory lung activity and to early identify patients with rapidly progressive lung disease. The latter remains to be determined in large, prospective comparative trials.

Elevated spleen FDG uptake predicts unfavorable outcome in adult idiopathic-inflammatory-myopathy patients: a crisis beyond muscles

BACKGROUND

Idiopathic inflammatory myopathy (IIM) is a group of autoimmune diseases that frequently leads to unfavorable outcome. This study aimed at identifying the clinical value of PET/CT scan in predicting the outcome of adult IIM patients.

METHODS

Adult IIM patients who were admitted to the four divisions of the First Affiliated Hospital, Zhejiang University School of Medicine (FAHZJU), from January 1, 2017, to December 31, 2020, were retrospectively reviewed. PET/CT scan and other factors of IIM patients who met the inclusion and exclusion criteria were collected and analyzed.

RESULTS

A total of 69 adult IIM patients were finally enrolled into this study. Thirty cases (43.5%) of all the patients enrolled died in follow-up, and the medium follow-up time was 11.90 (4.00, 23.80) months. In particular, 14 patients died within 3 months. The univariate Cox proportional hazards regression analyses revealed pulmonary bacterial infection (P < 0.001), rapidly progressive interstitial lung disease (RP-ILD, P = 0.018), maximum standard uptake value of spleen (spleen SUVmax, P = 0.002), and positivity of anti-MDA5 antibody (P = 0.041) were significantly related to survival in follow-up. The following multivariate Cox proportional hazards regression analysis identified pulmonary bacterial infection (P = 0.003) and spleen SUVmax (P = 0.032) as factors significantly associated with survival of IIM-ILD patients. The subsequent receiver operating characteristic curve analysis showed SUVmax was comparably effective in predicting death within 3 months.

CONCLUSION

Spleen SUVmax and complication of pulmonary bacterial infection were significantly associated with survival of IIM patients. In addition, elevated spleen SUVmax was efficient in predicting unfavorable outcome of adult IIM patients. Key Points • IIM is a group of autoimmune diseases that frequently leads to unfavorable outcome • Complications of splenic SUVmax and pulmonary bacterial infection were significantly associated with survival in IIM patients.

Radiological Characteristics of Patients With Anti-MDA5-Antibody-Positive Dermatomyositis in 18F-FDG PET/CT: A Pilot Study

Objective: To elucidate the ¹⁸F-fluorodeoxyglucose (FDG) PET/CT characteristics and its prognostic value in the patients with anti-melanoma differentiation associated protein 5 antibody positive (anti-MDA5+) dermatomyositis (DM). Methods: This retrospective cross-sectional study included 26 patients with anti-MDA5+ DM and 43 patients with anti-MDA5 negative (anti-MDA5-) idiopathic inflammatory myopathy (IIM) who were examined by ¹⁸F-FDG PET/CT from January 1, 2017 to December 31, 2020. The maximum standardized uptake value (SUVmax) of multiple organs and other clinical characteristics of the patients were measured and analyzed. Results: Compared with the anti-MDA5- group, the patients in the anti-MDA5+ group showed higher bilateral lung SUVmax (p = 0.029), higher SUVmax of spleen (p = 0.011), and bone marrow (p = 0.048). Significant correlations between the spleen SUVmax and serum ferritin levels (r = 0.398, p < 0.001), erythrocyte sedimentation rate (ESR) (r = 0.274, p = 0.023), platelet count (r = -0.265, p= 0.028), myositis disease activity assessment score (r = 0.332, p = 0.005), bone marrow SUVmax (r = 0.564, p < 0.001), and bilateral lung SUVmax (r = 0.393, p < 0.001) were observed. Conclusion: ¹⁸F-FDG PET/CT was found valuable in quantifying the pulmonary focal inflammation and potentially unveil the distinctive characteristics and pathophysiological mechanisms in the patients with anti-MDA5+ DM.