Bone marrow plasma cell infiltration in light chain amyloidosis: impact on organ involvement and outcome

Objectives: Prognosis of immunoglobulin light-chain (AL) amyloidosis depends mainly on the presence of cardiac involvement and the disease burden. A higher bone marrow plasma cell (BMPC) burden has been recognized as an adverse prognostic factor. The aim of our study was to analyze the correlation between the BMPC infiltration, clinical features and outcomes in patients with AL amyloidosis.

Methods: The clinical records of 79 patients with AL amyloidosis treated at a single institution.

Results: Median BMPC infiltration at diagnosis was 11% and significantly correlated with the serum free light-chain difference (p < .001). Patients with more than 10% BMPCs had more frequent cardiac involvement (86 vs. 63%; p = .015), a trend towards a higher early mortality (27 vs. 11%; p = .08) and a significantly shorter progression-free survival (PFS) (median of 18 vs. 48 months, p = .02) and overall survival (median of 33 months vs. not reached; p = .046). In the multivariate analysis, a BMPC infiltration over 10% retained its adverse prognostic value for PFS (HR = 2.26; 95% CI, 1.048-4.866; p = .038). The use of new drugs seemed to overcome the negative prognostic impact of a higher BMPC infiltration.

Conclusion: Higher BMPC infiltration in AL amyloidosis might be associated with increased systemic organ damage, particularly cardiac involvement and is rarely related to the development of myeloma features.