P896: value of 18f-fdg pet/ct in the evaluation of organ involvement in newly diagnosed primary systemic light chain amyloidosis

Topic: 14. Myeloma and other monoclonal gammopathies - Clinical Background: Positron emission tomography/computed tomography (PET/CT) can specifically accumulate imaging in tumor tissues.SUVmax is taken from the highest value of FDG uptake in the ROI of the fusion image and represent the metabolism of the target lesion.In our center, we used whole-body 18F-FDG PET/CT to differentiate occult multiple myeloma from pAL, during which we found that affected organs in patients with pAL showed hypermetabolism.In this study, we retrospectively analyzed 18F-FDG PET/CT findings and clinical parameters in 37 newly diagnosed pAL patients in order to investigate the value of 18F-FDG PET/CT for assessing organ involvement in pAL. Aims: To analyze the value of 18F-FDG PET/CT in the evaluation of systemic organ involvement in patients with newly diagnosed primary systemic light chain amyloidosis (pAL). Methods: The clinical data of 37 patients with newly diagnosed pAL admitted to the Department of Hematology of the First Affiliated Hospital, Sun Yat-sen University from October 2013 to June 2021 were retrospectively analyzed. The correlation between 18F-FDG PET/CT assessment and clinical criteria assessment of organ involvement were compared. The relationship between the maximum standardized uptake value (SUVmax), the SUVmax ratio of target organ to mediastinum blood pool (T/Mmax), the SUVmax ratio of target organ to liver blood pool(T/Lmax) and organ biological indicators, disease stage were analyzed. In our study, we focused on the relationship between cardiac biochemical parameters and cardiac FDG uptake. In addition, we analyzed the prognosis value of cardiac FDG uptake. Results: 37 patients with newly diagnosed pAL were included, with a mean age of 59.4±9.6 years. 18F-FDG uptake was observed positive in the heart (29 patients, 78.2%), kidney (16 patients, 43.2%), liver(12 patients, 32.4%), spleen(7 patients, 18.9%), intestine (23 patients, 62.2%), tongue (9 patients, 24.3%), and lung (9 patients, 24.3%). In the heart, liver, spleen and intestine, the positive rate of 18F-FDG PET/CT assessment was significantly higher than the clinical criteria, but 18F-FDG PET/CT assessment for the kidney, lung, tongue, nervous system and bone marrow has limitations. Quantitative analysis (target lesion SUVmax≥2.5) identifies organ involvement at more sites compared with clinical diagnostic criteria. Heart involvement on 18F-FDG PET/CT showed great correlations with the clinical assessment criteria. Patients with N-terminal pro-brain natriuretic peptide (NT-proBNP) ≥1800 pg/ml, interventricular septal (IVS) ≥12 mm, and left ventricular posterior wall (LVPW)≥12 mm showed a higher cardiac SUVmax, T/Mmax, and T/Lmax (p < 0.05). Patients with more advanced Mayo2004 stage, higher troponin T values (TNT), or smaller left ventricular ejection fraction had higher cardiac FDG uptake from a view of a general tendency. Combined cardiac FDG uptake with biochemical parameters could more accurately predict the prognosis of pAL, and are used to identify the patients with terminal stage. Patients with cardiac T/Lmax≥2.6, TNT > 0.035 ng/mL, and NT-proBNP > 332 ng/L had a worse prognosis (P < 0.001), with a median survival time of 6.9 months (See Figure1). Summary/Conclusion: Whole body 18F-FDG PET/CT, as a non-invasive diagnostic method, can comprehensively and intuitively assess systemic organ involvement. 18F-FDG uptake may be used as an indicator to assess organ involvement. Whole body 18F-FDG PET/CT, as a quantitative assessment tool at the organ level, is expected to be used for evaluating organ function accurately, making prediction of disease prognosis, and monitoring organic treatment response.Keywords: AL amyloidosis