Prognostic Significance of Circulating Plasma Cells by Multi-Parametric Flow Cytometry in Light Chain Amyloidosis

We evaluated the prognostic impact of clonal circulating plasma cells (cPCs) detected by six-color multi-parametric flow cytometry (MFC) in light chain (AL) amyloidosis at diagnosis. Of the 154 patients who underwent MFC, cPCs were detected in 42% (n = 65) patients. Median number of cPCs was 81 per 150 000 events (range: 6 – 17 844). High bone marrow plasma cell percentage was an independent predictor of presence of cPCs. Presence of cPCs at diagnosis was associated with inferior overall survival (OS) (90 vs. 98 months, p = 0.003) and inferior progression free survival (PFS) (31 vs. 52 months, p = 0.02). Estimated 1, 2 and 5 year OS in the two groups was: 74%, 64% and 57% and 89%, 87% and 80%, respectively. Estimated PFS at 1, 2 and 5 years was: 69%, 56% and 23% and 80%, 74% and 37%, respectively. Furthermore, the presence of cPCs at diagnosis was an independent adverse predictor of OS in multivariable analysis. Achieving a very good partial response or better was able to overcome the adverse impact of cPCs at diagnosis. Patients with cPCs at diagnosis may warrant closer monitoring post-treatment, especially if they do not achieve a deep hematologic response.