Correlation between Changes in Granzyme B Expression and Time to Progression in Patients with Newly Diagnosed Multiple Myeloma Treated with Lenalidomide and Dexamethasone Therapy

【Background】Triplet and quadruplet regimens of novel agents have improved the survival of patients with multiple myeloma (MM) and elicited deeper responses to treatment. Minimal residual disease (MRD) negativity is now used as a surrogate marker for longer progression-free survival. However, triplet and quadruplet regimens can cause severe toxicity especially for elderly frail patients and financial toxicity is now an issue. On the other hand, long duration of response is sometimes experienced to low-dose lenalidomide and dexamethasone (Ld) therapy. However, the predictors of long duration of response is unknown. Sustained response without severe toxicity even if not achieving the MRD negativity is beneficial in the treatment choice for some populations like frail elderly patients. Therefore, predicting the long-duration of response could lead to individualized therapy, reducing overtreatment. Here, we hypothesized that the immunomodulatory effects of lenalidomide correlates with a long duration of response.

【Methods】We have previously conducted a prospective trial of Ld therapy in 40 patients with newly diagnosed transplant-ineligible MM. Among them, the time to progression (TTP) was evaluated in 29 patients, excluding patients who discontinued Ld therapy before disease progression. In this study, we evaluated the correlation between immune profile changes and TTP in this study set. Immune profile was evaluated by flow cytometry using peripheral blood mononuclear cells (PBMCs) obtained before and during the first or second cycles of Ld therapy. We evaluated the T cell subset (CD4+ T cells, CD8+ T cells, regulatory T cells) and NK cells and NKT cells and myeloid-derived suppressor cells. Exhaustion markers of PD-1, Tim-3, CTLA-4 and the activation markers of 4-1BB in each lymphocyte subset and memory subset of T cells were evaluated. The cytokine production of granzyme B, IFN-γ, TNF-α and IL-2, was detected by intracellular cytokine staining after 6-h stimulation with phorbol 12-myristate 13-acetate (25 ng/mL) and ionomycin (1 μg/mL) in the presence of the protein transport inhibitor, Golgi stop (BD Bioscience).

【Results】The median age was 75 years old (range, 61-86) at the initiation of Ld therapy. Median TTP was 34 months (range, 1-70). We divided the cases into two groups using the median TTP as a cut-off point (Figure 1). There were no significant differences in baseline characteristics, male to female ratio, performance status, M-protein subtype, creatinine clearance, international staging system (ISS), and high risk cytogenetic profiles between these two subgroups, except for age (median age was 77 years old in subgroups with TTP < 34 months compared to 72 years old, p=0.04). Median initial dosage of lenalidomide was not statistically different (10 mg/day and 15 mg/day in subgroups with TTP < 34months and TTP > 34months, respectively) and dexamethasone dosage was 20 mg/day in both groups. The achievement of best response more than partial response was also comparable in both subgroups (71% and 93% in subgroups of TTP < 34months and TTP > 34months). We compared the immune profile changes in these subgroups. Consequently, we found that mean fluorescence intensity (MFI) ratio of granzyme B expression in NK and NKT cells (before and after Ld therapy) and ΔMFI of granzyme B expression in CD8+ T cells were significantly higher (p<0.05) in longer TTP subgroups (Figure 2).

【Conclusions】Our data suggest that early immune responses during the first or second cycle of Ld therapy could serve as the predictive marker of longer TTP following Ld therapy in patients with NDMM. This could benefit some patients, particularly frail elderly patients by helping them avoid unnecessary intensification of treatment.

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