The clinical significance of CD49e and CD56 for multiple myeloma in the novel agents era

Multiple myeloma (MM) is a hematological malignancy characterized by the proliferation of abnormal plasma cells in bone marrow. Flow cytometry distinguishes between normal and abnormal plasma cells by evaluating cluster of differentiation (CD) 56 and CD19 expression patterns. Moreover, immunophenotyping of mature plasma cell 1 (MPC-1) and very late antigen-5 (CD49e) identifies the maturity of MM as mature (MPC-1⁺, CD49e⁺), intermediate (MPC-1⁺, CD49e^–), or immature (MPC-1^–, CD49e^–). We retrospectively examined the effects of surface marker expression and maturity subtype on overall survival (OS) and time to next treatment (TNT) among 55 patients (25 males, 30 females) with symptomatic MM. All patients were treated with regimens containing bortezomib (BOR) (n = 39) or lenalidomide (LEN) (n = 16) as the initial treatment. Median age at diagnosis was 72 years (range: 36–88). The lack of CD56, an aberrant marker, was associated with significantly worse prognosis compared with CD56⁺ MM (median OS: 24 vs. 60 months, respectively; p = 0.0050). In CD49e⁺ MM, defined as mature type, no significant difference was seen in TNT of the initial treatment, regardless of whether it was a BOR-based regimen or LEN + dexamethasone (Ld) therapy. On the other hand, in CD49e^– MM, defined as immature/intermediate type, TNT of Ld therapy was significantly longer than that of BOR-based regimens (median TNT: undefined vs. 12 months, respectively; p = 0.0043). These results suggest that Ld therapy is more effective than BOR-based therapy for CD49e^– MM and thus may aid regimen-related decisions in the novel agents era.