Bone marrow plasma cells 20% or greater discriminate presentation, response, and survival in AL amyloidosis.

We explored the association between bone marrow plasma cells (BMPCs) and disease presentation and outcome among 1574 AL patients. Three BMPC groups were formulated: <5% (n = 231, 15% of study population), 5-19% (n = 1045, 66%), and ≥20% (n = 298, 19%). Heart and renal involvement were more and less prevalent, respectively, with increasing BMPCs. Patients with ≥20% BMPCs had higher likelihood for classic myeloma phenotype with less skewed lambda restriction, a higher rate of intact immunoglobulin secretion, a lower hemoglobin and higher rates of hypercalcemia and bone lytic lesions. High-risk cytogenetic abnormalities were more common in ≥20% BMPCs. Complete hematological response was less frequent with rising BMPCs. The median survival was inversely associated with the BMPC groups (81, 33, 12 months for <5%, 5-19%, and ≥20% BMPCs, respectively; P < 0.001). Survival discrimination was maintained at 1-year landmark and in those who achieved a complete response. Multivariate analysis accounting for known prognostic markers yielded an independent prognostic role for ≥20% BMPCs, but not for the other BMPC groups. AL patients with 20% or greater BMPCs have poorer outcome independent of their cardiac risk category and stem cell transplant eligibility. Distinct interventions in these patients should be explored to improve outcome.