Impact of lenalidomide and dexamethasone treatment on immune cell populations of the patients with refractory/relapsed multiple myeloma

Background: Lenalidomide combined with low-dose dexamethasone (Len-dex) is an effective treatment for the patients with refractory/relapsed multiple myeloma (RRMM). The anti-myeloma effect of lenalidomide is associated with activation of the immune system, but the exact immunomodulatory mechanisms in vivo and clinical impact of Len/dex in RRMM patients remains unclear. In this study, we analyzed immune cell populations in patients receiving Len-dex for the treatment of RRMM. Methods: Peripheral blood samples from 90 RRMM patients were taken on day 1 of cycles 1 (baseline), 2, 3, and 4 of Len/dex therapy. CD3+, CD4+, CD8+, CD161+ T cells, natural killer (NK) cell (CD16+/CD56+), NKT-like cell (CD3+/CD56+) and myeloid-derived suppressor cell (MDSC) including granulocytic (G-MDSC) and monocytic (M-MDSC) were analyzed by flow cytometry. In addition, response was assessed in 81 patients receiving more than 4 cycles of Len-dex and the comparison of cell populations according to an achievement of ≥very good partial response (VGPR) was performed. Results: Forty-eight men and 42 women were enrolled in this study. The median age was 61 years (range, 29-84 years). At baseline, peripheral blood CD3+ cell frequency was 51.65 ± 1.79% which was significantly decreased to 41.67 ± 2.44% (P=0.001) and 39.72 ± 2.90% (P Conclusion: Our data demonstrate that Len-dex therapy in patients with RRMM is associated with decreased frequency of T cells with a trend of increased NK cell frequency. Change in CD8+ cell and M-MDSC frequency can correlate with the quality of response to Len-dex. Baseline NKT-like cell frequency and change in CD3+ and CD8+ cells early after treatment may predict continuation of anti-myeloma effect of Len-dex therapy. Disclosures No relevant conflicts of interest to declare.