Lenalidomide Consolidation Followed by Maintenance After Autologous Transplantation for Multiple Myeloma Decreases Thymic Output and Terminally Differentiated CD4 and CD8 T Cells but Increases Treg

Abstract 4046

Treatment with lenalidomide, an immunomodulatory drug, increases the time to progression in relapsed/refractory multiple myeloma. However, due to its pleiotropic effect, it is not known whether the efficacy of this drug is due only to direct tumor toxicity or also to immunomodulatory effects. We assessed in vivo the changes in T-cell reconstitution induced by lenalidomide consolidation and maintenance treatment following autologous peripheral blood stem cell transplantation (ASCT) in a cohort of multiple myeloma patients.

Twenty-nine newly diagnosed myeloma patients were treated with the induction combination bortezomib plus dex followed by high dose melphalan (140–200 mg/m²) and ASCT. A first group of 11 patients were treated with lenalidomide consolidation initiated 3 to 6 months post transplantation: 25 mg/day, days 1–21 of a 28 day cycle for 2 months, followed by maintenance (10 mg/day) until disease progression. This group was compared with the 18 patients who did not receive any treatment after ASCT. Blood samples were collected at diagnosis, before the transplant and 1, 3, 6, 9, 12 and 18 months after ASCT. Thymic function was assessed by real-time PCR quantification of T cell receptor excision circles (sjTREC) and percentages and absolute counts of T lymphocyte subpopulations were determined by multicolor flow cytometry. Statistics were performed using the Log-Rank or Mann-Whitney test.

The two cohorts had similar baseline characteristics and all 29 patients were in remission after ASCT. With a median follow-up of 4 years, progression-free survival (PFS) was superior with lenalidomide treatment (69% vs 36%, p=0.05) while overall survival (OS) was similar (82% vs 75%, p=0.5). Lenalidomide treatment induced a progressive decrease in sjTREC (median at 18 months, 0.25/μL vs 1.61/μL, p<0.05) and a decrease in the percentages and absolute counts of CD4+ and CD8+ CD45RA+CCR7- effector terminal T cell subpopulations (median at 18 months, 3.2/μL vs 17.6/μL, p<0.05 for CD4+CD45RA+CCR7- and 109/μL vs 345/μL, p<0.05 for CD8+CD45RA+CCR7-). Conversely, lenalidomide treated patients displayed an increase in CD4+CD25+CD127-/low Treg populations, in both percentage and absolute count (median 13% vs 8 %, p<0.05 and 48.9/μL vs 29.3/μL, p<0.05, respectively). No correlation was found with documented infections, relapse or survival.

We confirm an increase in PFS with lenalidomide consolidation/maintenance following ASCT. However, our data also suggest that in myeloma patients, the effect of lenalidomide on the myeloma tumor may not be T cell mediated and this treatment may have a negative impact on the T cell immune surveillance.