Composition of the Immune Environment at Baseline Correlates with Time to Response and Treatment Outcome in Newly Diagnosed Transplant-Ineligible Multiple Myeloma (MM) Patients Randomized to Krd or Ktd Followed By Carfilzomib Maintenance or Observation (AGMT_MM 02 Study)

Background

Rapid induction of remission is a favorable factor in pts with Hodgkin's disease and DLBCL. In MM, only few data are available on the impact of response kinetics on outcome in newly diagnosed transplant ineligible MM pts. Recently, (Abstract EP971, EHA 2021) we described a significant correlation between time to response and progression-free survival (PFS) and overall survival in this patient population.

Response and time to response depend on several factors such as the biology of the underlying myeloma clone(s), the activity of the treatment regimen, and on the composition of the bone marrow immune environment. Here, we evaluated possible interconnections between the bone marrow immune environment at baseline and the time to response to therapy in a series of pts randomized to either 9 cycles KRd or KTd induction therapy followed by a second randomization to carfilzomib maintenance or observation.

Patients and Methods

Composition of the immune environment at baseline was analyzed in 55 pts with newly diagnosed transplant ineligible MM enrolled in a randomized phase II trial (AGMT_MM 02). Median age: 74 years (range: 58-84 years), ISS I: 21.8%, ISS II: 41.8%, and ISS III: 36.4%, cytogenetics: 30.9% high risk, 40% standard risk, 29.1% unknown, ECOG Status 0: 54.5%, 1: 45.6%. Treatment: Carfilzomib : Cycle 1 day 1+2: 20mg/m ², days 8+9 and 15+16: 27 mg/m ² ; Cycle 2 day 1,2,8,9,15 + 16: 27 mg/m ² Cycle 3-9: 56mg/m ² on days 1, 8 and 15. Lenalidomide: 25mg p.o. on days 1-21/cycle or thalidomide: 100 mg p.o. on days 1-28; in pts ≥75 years of age 50mg p.o. on days 1-28, dexamethasone: 40 mg p.o. on days 1, 8, 15, 22 (± 1 day), in pts ≥ 75 years of age 20 mg p.o. this treatment was administered for nine cycles. Thereafter, pts were randomized to carfilzomib maintenance at last tolerated dose on days 1+15 or to observation for 12 cycles.

BM samples were stained with 3 different antibody combinations for the analysis of T, B and NK cells (T cells: CD45RA, CD127, CD8, TCRgd, CD25, CD197, CD4, CD3, B/NK cells: CD57, CCR7, CD314, CD85j, CD62L, CD3, CD16, CD56, CD335, HLADR, CD337). We used a semi-automated pipeline to unveil full cellular diversity based on unbiased clustering. The median and range of each cellular subgroup was calculated and compared between pts with short or longer time to response (< or ≥119 days (median)). Statistical significance of these comparisons was calculated using the Wilcoxon test.

Results

Median FU was 20.5 months. Twenty of the 55 pts achieved a CR (36.7%) and 16 (57.1%) of the 28 who had MRD testing were shown to be MRD negative at a sensitivity of 10 ^-6. Twenty-three pts achieved a VGPR (41.8%), while only 12 pts achieved a PR (21.8%). Pts were subdivided into two groups according to time to best response. Group A (n=26), median time 56 (26-112) days, group B (n=29), 265 (119-675) days. PFS was significantly longer in group B (19.1 months vs not reached, p=0.007), while for OS only a trend for better survival was noted for group B pts (median survival not reached, p=0.129).

High numbers of total CD3 ⁺ cells (p=0.033) and CD4 T cells with a CD 197 ^loCD45RA ^-CD127 ⁺ phenotype (p=0.022) were associated with longer time to best response and longer PFS. An opposite result was noted for the following T cell subsets, which correlated with a shorter time to best response and shorter PFS: CD56 ⁺ T cells with (p=0.01) or without (p=0.024) HLADR and CD8 Naïve CD127 ⁺ T cells (p=0.041). Diverse results were noted when the NK cell compartment was analyzed. Higher levels of circulatory CD314 ^- (p<0.0001) and circulatory CD314 ⁺ (p=0.049) NK cells correlated with longer time to best response and longer PFS. By contrast, lower levels of cytotoxic HLADR ⁺ NK cells (p=0.044) were associated with better outcome.

Conclusion

Our data show significant correlations between the composition of bone marrow immune cells at start of therapy with time to best response and PFS in newly diagnosed transplant ineligible MM pts uniformly treated with carfilzomib-based therapy. High numbers of total lymphocytes CD3 and CD4 Tcells with a CD197 ^loCD45RA ^-CD127 ⁺ phenotype correlated with significantly longer PFS and longer time to response. Furthermore, higher numbers of specific NK subsets such as those with a circulatory phenotype, correlated with better outcome. These results highlight the prognostic potential of immune monitoring and the interconnection between specific subsets of the immune environment with the course of the disease.

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