Serial serum FLC and NT-ProBNP concentration. Each line represents a single patient. Open symbols represent patients alive at censor; filled symbols, patients who had died. (A) Response of the FLC concentration to chemotherapy. FLC concentration decreased after SCT to less than 50% of pretreatment levels in 4 patients. Patient 3 experienced a decrease in FLC concentration after heart transplantation and before SCT that was further consolidated by SCT. Patient 2 had a poor initial FLC response to SCT and then had a relapse but responded to high-dose dexamethasone therapy (arrow). Patients 1 and 4 experienced FLC relapse associated with progressive intracardiac and extracardiac amyloid accumulation and died. (B) Serial serum NT-proBNP concentration decreased after heart transplantation (timing indicated between the dotted vertical lines) in the 4 patients in whom it was measured. Relapse of the plasma cell dyscrasia and accumulation of amyloid in the cardiac allograft and major viscera in 2 patients were associated with a marked increase in NT-ProBNP concentration and patient death.