Minimal Residual Disease Analysis in Multiple Myeloma Patients By 6-Color Flow Cytometry: An Experience from Tertiary Care Center of North India

Therapeutic advances in multiple myeloma (MM) incorporating the use of high-dose melphalan, novel therapeutic immunomodulatory agents, proteasome inhibitors and supporting autologous stem-cell transplantation (ASCT) have improved response rates and overall survival. The detection of minimal residual disease (MRD) is recognized as a sensitive and rapid approach to evaluate treatment efficacy as a tool for predicting patient outcomes and guiding therapeutic decisions. MRD analysis is reflected by many different techniques, however, multiparametric flow cytometry is a sensitive, feasible and adequate method for monitoring residual disease. Studies from India related to this context are lacking. In the present study, we compare MRD levels in patients of multiple myeloma after chemotherapy/ASCT assessed by multiparametric flow cytometry, with M band status, immunofixation (IFE) and percentage of plasma cells on bone marrow aspirate.

Seventeen patients of multiple myeloma were included in the study over a duration of one year, (Male=13, Female=4) with mean age of 56.8 years (range 44-80 years). MRD was analyzed using a dual laser 6 color-flow cytometer in 9 patients of ASCT (day 100) and 8 patients on chemotherapy alone (post-induction). Pre-titrated cocktail of CD38, CD138, CD19, CD45, cytoplasmic Kappa light chain, cytoplasmic lambda light chain, CD81, CD27, CD28 CD200 and CD10 were used in 6-color combination of three tubes for MRD analysis. MRD was detectable in 5 patients, mean of 0.61% (range of 0.07 - 6.44%). M band and IFE were positive in 2 patients, each. Bone marrow plasma cells ranged from 0 to 22%. MRD levels did not show significant correlation with percentage of plasma cells in bone marrow aspirate, however it had an statistical agreement with presence or absence of serum M-band and IFE. Patients are on regular follow up for their clinical and hematological response.