Molecular Imaging of the Underlying Mechanism of Cardiotoxicity in Patients With Light Chain Amyloidosis Using PET/CT

Immunoglobulin light chain (LC) amyloidosis (AL) is an underdiagnosed monoclonal plasma cell proliferative disorder caused by extracellular deposition of AL fibrils in various tissues and organs, causing disease by progressively damaging the structure and function of the affected tissue/organ. The heart is the most commonly involved organ (\~75%),9 and the extent and severity of cardiac involvement continue to be the main limitation for successful treatment. Although it remains high, the 6-month mortality rate has improved significantly over the last decade (24% vs. 37%; P\<0.001) due to earlier diagnosis, better treatment options, and the advent of sensitive serologic biomarkers to assess for early treatment response,10 in particular serum free light chains (FLC), which permit the differentiation of patients who achieve complete response (CR) and very good partial response (VGPR) from those with partial or no response. N-terminal fragment of the pro-brain natriuretic peptide (NT-proBNP) has also become a key biomarker for detection and risk-stratification of patients with cardiac AL amyloidosis, and is now routinely employed in clinical trials as a surrogate end point for survival. A large retrospective landmark analysis established that achievement of a CR or VGPR at 6 months post-initiation of therapy, or achievement of an NTproBNP response 6 months post-initiation of therapy, defined as a 30% reduction and absolute reduction ≥ 300 pg/mL from baseline for subjects with baseline levels ≥ 650 pg/mL, was strongly associated with improved overall survival (insert Palladini et al, JCO 2012).