Development and validation of a survival staging system incorporating BNP in patients with light chain amyloidosis.

Immunoglobulin light chain amyloidosis (AL amyloidosis) is caused by misfolded light chains that form soluble toxic aggregates that deposit in tissues and organs, leading to organ dysfunction. The leading determinant of survival is cardiac involvement. Current staging systems use N-terminal pro-brain natriuretic peptide (NT-proBNP) and cardiac troponins T and I (TnT and TnI) for prognostication, but many centers do not offer NT-proBNP. We sought to derive a new staging system using brain natriuretic peptide (BNP) that would correlate with the Mayo 2004 staging system and be predictive for survival in AL amyloidosis. Two cohorts of patients were created: a derivation cohort of 249 consecutive patients who had BNP, NT-proBNP, and TnI drawn simultaneously to create the staging system and a complementary cohort of 592 patients with 10 years of follow-up to determine survival. In the derivation cohort, we found that a BNP threshold of more than 81 pg/mL best associated with Mayo 2004 stage and also best identified cardiac involvement. Three stages were developed based on a BNP higher than 81 pg/mL and a TnI higher than 0.1 ng/mL and compared with Mayo 2004 with high concordance (κ = 0.854). In the complementary cohort, 25% of patients had stage I, 44% had stage II, 15% had stage III, and 16% had stage IIIb disease with a median survival not reached in stage I, 9.4 years in stage II, 4.3 years in stage III, and 1 year in stage IIIb. This new Boston University biomarker scoring system will allow centers without access to NT-proBNP the ability to appropriately stage patients with AL amyloidosis. This trial was registered at www.clinicaltrials.gov as #NCT00898235.