Clinical Implication of Minimal Residual Disease By Multiparameter Flow Cytometry in Light Chain Amyloidosis

We evaluated bone marrow minimal residual disease (MRD) by multiparameter flow cytometry (sensitivity 10 ^-5) in 91 patients with light chain amyloidosis (AL). The overall MRD negative rate was 42.9% (n=39). The MRD negative rate among patients in complete response, very good partial response, and less than PR was 61.5% (24/39), 35.7% (10/28), and 0% (0/11), respectively. There were no significant differences in baseline characteristics regarding age, light chain burden, and organ involvement, while lower proportion of male sex and cytogenetics t(11;14) by FISH was observed in MRD negative patients. Patients with MRD negativity had a numerically higher proportion of cardiac response (54.8% vs 40.5%, P=0.224) and renal response (52.6% vs 41.7%, P=0.474). After a median follow-up time of 29.0 months, patients with MRD negativity had a near significantly longer event-free survival (EFS, defined as hematological progression/organ dysfunction/initiation of next-line therapy and death) from treatment initiation than patients with MRD positivity (NR vs 38.8 months, P=0.078). The 5-year overall survival (OS) for patients with MRD negativity and MRD positivity were 82.7% and 67.8%, respectively (P=0.229).