Background Amyloidosis comprises a group of diseases characterized by a deposition of amyloid fibrils which have an antiparallel B-sheet secondary structure. Active research in seeking evolution of deposits must be done regularly with several tests. FBP is a radiotracer with tropism to proteins with β-sheet conformation that is used in Alzheimer's disease1.
Objectives The purpose of this study was to evaluate the utility of FBP in studying the extension of the amyloidosis.
Methods We performed an observational descriptive study with 14 subjects controlled at our Amyloidosis Unit: twelve patients with a biopsy-proven disease, one patient with senile amyloidosis and one woman with a familiar TTR mutation without evidence of diposits. Study was conducted from February 2015 until August 2015. A PET/CT was performed with injection of 370MBq FBP. Images were acquired after 40–50 minutes of injection and a qualitative description was done. Evaluation also included traditional techniques like echocardiogram, cardiac MRI, blood and urine tests, and electromyography. If other organs were involved, they were registered. The correlation between traditional techniques and PET/CT was studied.
Results The median age at diagnosis was 69 years (IQR: 60 – 75) and the median follow up 22.2 months (IQR 2 – 32). Two patients had hereditary amyloidosis by transthyrretin (TTR), 1 patient a senile amyloidosis, 8 patients a primary amyloidosis and 2 a secondary amyloidosis. Traditional evaluation detected heart involvement in 9 patients (69.23%), kidney involvement in 6 (46.15%) and soft tissue was involved in 4 patients (30.76%): 2 of them had macroglossia, 1 patient had thyroid gland amyloidosis and the remaining one had amyloid deposits in the stomach.
PET/CT showed cardiac involvement in 8 patients (61.53%), kidney in 3 patients (23.07%) and soft tissue in 6 (46.15%) patients: tongue in 2 patients, thyroid gland in 2, spleen in 1, lungs in 2. Multiple organs were involved in 4 patients (30.76%).
Correlation between traditional techniques and PET/CT showed that 6 patients had both positive tests for heart involvement. Two patients identified as having cardiac amyloidosis by echocardiogram and cardiac MRI had a negative PET. Two patients with a positive PET had a negative cardiac MRI but echocardiogram showed left ventricular hypertrofia. Kidney involvement was present in 3 patients with a previously known renal disease (50% of patients). Soft tissue involvement showed an increased uptake in the tongue in the two patients with macroglossia, thyroid involvement in the patient with goiter but didn't show gastric involvement in the remaining patient. Two subjects had bilateral lung involvement which was not previously suspected and another patient had thyroid and spleen involvement. The healthy subject (affected by the familial TTR mutation) had a normal PET/CT.
Conclusions FBP PET/CT is a promising technique to evaluate the number of organs affected in patients with amyloidosis. Prospective studies with bigger cohorts are required to validate its use during our clinical practice.
Lin KJ, Hsu WC, Hsiao IT et al. Whole-body biodistribution and brain PET imaging with [18F]AV-45, a novel amyloid imaging agent–a pilot study. Nucl Med Biol. 2010;37:497–508.
Disclosure of Interest None declared