Utility of Immunophenotyping at Diagnosis in Multiple Myeloma-an Observational Study from a Tertiary Care Center in India

Introduction and Aims: Flow cytometry (FCM) has been useful in differentiating abnormal plasma cells (APCs) from normal plasma cells (NPCs) based on the different surface antigen expressions as well as the clonality analysis. The enumeration of NPCs and APCs is of prognostic significance. The phenotypic expressions of different antigens have been found prognostically relevant in myeloma. We intended to evaluate the prognostic significance and utility of immunophenotyping of multiple myeloma (MM) cases at diagnosis.

Materials and Methods: We evaluated 48 newly diagnosed MM cases. Immunophenotyping was done by a 3-tube 6-color FCM panel. NPCs and APCs were defined based on light chain restriction and immunophenotypic aberrancies.

Results: Cases with >3% NPCs did not show a RISS3 disease (P=0.024). Cases with <3% NPCs at diagnosis were predominantly ISS2 or ISS 3 disease. Cases with >3% NPCs in bone marrow presented with a higher hemoglobin (P=0.004), lower creatinine (P=0.035) and lower beta-2 microglobulin (P=0.003) compared to cases with <3% NPCs at diagnosis.

Conclusion: Cases with increased number of NPCs at diagnosis are associated with good risk factors and may fare well after treatment. A diagnostic immunophenotyping should be encouraged to find out sub-groups of MM patients with higher NPCs.