Extracardiac 18F-florbetapir imaging in patients with systemic amyloidosis: more than hearts and minds

Abstract

Purpose18F-Florbetapir has been reported to show cardiac uptake in patients with systemic light-chain amyloidosis (AL). This study systematically assessed uptake of 18F-florbetapir in patients with proven systemic amyloidosis at sites outside the heart.MethodsSeventeen patients with proven cardiac amyloidosis underwent 18F-florbetapir PET/CT imaging, 15 with AL and 2 with transthyretin amyloidosis (ATTR). Three patients had repeat scans. All patients had protocolized assessment at the UK National Amyloidosis Centre including imaging with 123I-serum amyloid P component (SAP). 18F-Florbetapir images were assessed for areas of increased tracer accumulation and time–uptake curves in terms of standardized uptake values (SUVmean) were produced.ResultsAll 17 patients showed 18F-florbetapir uptake at one or more extracardiac sites. Uptake was seen in the spleen in 6 patients (35%; 6 of 9, 67%, with splenic involvement on 123I-SAP scintigraphy), in the fat in 11 (65%), in the tongue in 8 (47%), in the parotids in 8 (47%), in the masticatory muscles in 7 (41%), in the lungs in 3 (18%), and in the kidney in 2 (12%) on the late half-body images. The 18F-florbetapir spleen retention index (SRI) was calculated. SRI >0.045 had 100% sensitivity/sensitivity (in relation to 123I-SAP splenic uptake, the current standard) in detecting splenic amyloid on dynamic imaging and a sensitivity of 66.7% and a specificity of 100% on the late half-body images. Intense lung uptake was seen in three patients, one of whom had lung interstitial infiltration suggestive of amyloid deposition on previous high-resolution CT. Repeat imaging showed a stable appearance in all three patients suggesting no early impact of treatment response.Conclusion18F-Florbetapir PET/CT is a promising tool for the detection of extracardiac sites of amyloid deposition. The combination of uptake in the heart and uptake in the spleen on 18F-florbetapir PET/CT, a hallmark of AL, suggests that this tracer holds promise as a screening tool for AL.Electronic supplementary materialThe online version of this article (10.1007/s00259-018-3995-2) contains supplementary material, which is available to authorized users.

ASNC/AHA/ASE/EANM/HFSA/ISA/SCMR/SNMMI Expert Consensus Recommendations for Multimodality Imaging in Cardiac Amyloidosis: Part 1 of 2—Evidence Base and Standardized Methods of Imaging

“…(95) Although not studied serially, retention of 11 C-PIB was lower in AL cardiac amyloidosis patients treated with chemotherapy as compared to those who did not undergo treatment, (127) suggesting it is possible this radiotracer will be useful for disease monitoring. Finally, unlike echocardiography or CMR, amyloid-binding PET tracers can image systemic amyloid deposits in various other organs (128,129) and offer the potential to quantify the load of amyloidosis in the whole body.…”

Early Detection of Multiorgan Light-Chain Amyloidosis by Whole-Body 18F-Florbetapir PET/CT

“…Three smaller observational studies have explored whole-body radiotracer detection of amyloid fibrils in subjects with AL and transthyretin amyloidosis. One study used 11 C-Pittsburgh compound B (n 5 7 AL subjects) (18), another study used 18 F-florbetapir (n 5 15 AL subjects) (19), and a final study used 18 F-florbetaben (n 5 7 AL subjects) (20). Although direct comparison of proportions of involved organs is difficult given the small sample sizes in prior studies and the heterogeneity of organs examined, when overlapping organs studied in these papers were evaluated, the results among the 4 studies were similar.…”

Blood-based protein mediators of senility with replications across biofluids and cohorts

“…SAP is co-localized with a variety of amyloids, including both Aβ 1 – 42 and amylin. It co-localizes with florbetapir both in and outside the CNS ( Wagner et al , 2018 ). SAP is thought to accelerate Aβ 1 – 42 deposition in NP ( Hamazaki, 1995 ; Tennent et al , 1995 ).…”