Curative Strategy (GEM-CESAR) for High-Risk Smoldering Myeloma (SMM): Carfilzomib, Lenalidomide and Dexamethasone (KRd) As Induction Followed By HDT-ASCT, Consolidation with Krd and Maintenance with Rd

Introduction: SMM is an asymptomatic plasma cell disorder with heterogeneous clinical behavior. Both the Spanish Myeloma and ECOG Groups have demonstrated that patients (pts) at high risk of progression to active MM have prolonged time-to progression upon receiving early treatment with R-based regimens. Our next step was to perform a phase 2, single arm trial, focusing on the same population, but aiming at abrogating the risk of progression through the achievement of sustained minimal residual disease negativity (MRD-ve) at 3 and 5 years after HDT-ASCT. Patients and methods: Ninety SMM pts at high-risk of progression (>50% at 2 yrs), younger than 70 years and transplant candidates were included. The high risk was defined by the presence of both ≥PC 10% and MC ≥3g/dL (Mayo criteria) or ifonly one criterion was present, pts should have >95%of aberrant PCs within the total PCsBM compartment by immunophenotyping plus immunoparesis (Spanish criteria). Induction therapy consisted of six 4-weeks cycles of KRd in which K was given at dose of 36 mg/m 2 twice per week plus R at dose of 25 mg on days 1-21 and dexamethasone at dose of 40 mg weekly. Melphalan at dose of 200 mg/m 2 followed by ASCT was given as intensification therapy followed by two KRd consolidation cycles and maintenance with R at dose of 10 mg plus dexamethasone at dose of 20 mg weekly for up to 2 yrs. The primary end-point was to evaluate the MRD-ve rate by next generation flow (NGF) after ASCT and MRD-ve rate maintained at 3 and 5 years after ASCT. Results: Between June 2015 and June 2017, 90 high-risk SMM pts were recruited and 70 pts (78%) have completed the treatment protocol. The reasons for early discontinuations were: IC withdrawal (4 pts), adverse events (8 pts) or biological progression (BP), either biochemical or because of MRD conversion from negative to positive (1 pt during induction and 7 pts during maintenance). Thirty-one pts (34%) shared at least one of the biomarkers considered as myeloma defining events that currently reclassify SMM into active MM. In the intent-to-treat (ITT) pts' population, after induction, the ≥CR rate was 41% and increased to 65% after HDT-ASCT and 72% after consolidation. During maintenance therapy, 7 pts experienced biological progression (2 pts conversion from MRD-ve into +ve and 5 pts biochemical progression) and the ≥CR rate at the end of treatment was 63.3%. In the ITT population, MRD-ve rates at 10 -5 were observed in 40% of pts after induction, 63% a