PURPOSE Assessing measurable residual disease (MRD) has become standard with many tumors, but the clinical meaning of MRD in multiple myeloma (MM) remains uncertain, particularly when assessed by next-generation flow (NGF) cytometry. Thus, we aimed to determine the applicability and sensitivity of the flow MRD-negative criterion defined by the International Myeloma Working Group (IMWG). PATIENTS AND METHODS In the PETHEMA/GEM2012MENOS65 trial, 458 patients with newly diagnosed MM had longitudinal assessment of MRD after six induction cycles with bortezomib, lenalidomide, and dexamethasone (VRD), autologous transplantation, and two consolidation courses with VRD. MRD was assessed in 1,100 bone marrow samples from 397 patients; the 61 patients without MRD data discontinued treatment during induction and were considered MRD positive for intent-to-treat analysis. The median limit of detection achieved by NGF was 2.9 × 10−6. Patients received maintenance (lenalidomide ± ixazomib) according to the companion PETHEMA/GEM2014MAIN trial. RESULTS Overall, 205 (45%) of 458 patients had undetectable MRD after consolidation, and only 14 of them (7%) have experienced progression thus far; seven of these 14 displayed extraosseous plasmacytomas at diagnosis and/or relapse. Using time-dependent analysis, patients with undetectable MRD had an 82% reduction in the risk of progression or death (hazard ratio, 0.18; 95% CI, 0.11 to 0.30; P < .001) and an 88% reduction in the risk of death (hazard ratio, 0.12; 95% CI, 0.05 to 0.29; P < .001). Timing of undetectable MRD (after induction v intensification) had no impact on patient survival. Attaining undetectable MRD overcame poor prognostic features at diagnosis, including high-risk cytogenetics. By contrast, patients with Revised International Staging System III status and positive MRD had dismal progression-free and overall survivals (median, 14 and 17 months, respectively). Maintenance increased the rate of undetectable MRD by 17%. CONCLUSION The IMWG flow MRD-negative response criterion is highly applicable and sensitive to evaluate treatment efficacy in MM.

Key PointsVRD was effective and well tolerated before ASCT; 33.4% complete response/28.8% minimal residual disease–negative after 6 induction cycles. Responses deepened with VRD throughout induction and over the course of treatment with few discontinuations due to toxicity.

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This study was conducted to determine whether the integration of the Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI) and the European Group for Blood and Marrow Transplantation (EBMT) score would improve individual capacity for stratification of high-risk HCT candidates. A total of 442 consecutive patients receiving an allogeneic HCT after reduced-toxicity conditioning was included. Final HCT-CI and EBMT scores were calculated and validated. Then, patients were grouped into a 6-category new combination model according to the HCT-CI (0, 1 to 2, ≥ 3) and EBMT scores (0 to 3, 4 to 7), and the model's predictive capacity was also evaluated. Median HCT-CI and EBMT scores were 3 and 4, respectively. Increased HCT-CI was associated with higher 4-year nonrelapse mortality (NRM) and lower 4-year overall survival (OS), whereas a high EBMT score was associated with higher 4-year NRM. The HCT-CI showed a trend for a better predictive capacity than the EBMT score (c-statistic .6 versus .54, P = .1). According to the new model, patients within HCT-CI of 0 and HCT-CI of 1 to 2 groups had similar risk of NRM independently of their EBMT score. Within the HCT-CI ≥ 3 group, patients with low EBMT score showed lower NRM (25% versus 40%, P = .04) and a trend to higher OS (52% versus 36%, P = .06) than patients with a high EBMT score. Moreover, patients with HCT-CI ≥ 3 and EBMT score 0 to 3 had similar outcomes than those with HCT-CI of 1 to 2. In conclusion, the combination of HCT-CI and the EBMT score is feasible and might contribute to a better identification of high-risk patients, improving selection of best allogeneic HCT candidates.

We report a patient with multiple myeloma presenting with a paraspinal plasmacytoma with a marked dissociation between the response obtained in bone marrow (BM) infiltration and that achieved in soft tissue masses. While a complete remission was reached and maintained in BM, extramedullary plasmacytomas were refractory to every line of treatment. Genetic analysis identified the presence of t(4;14) and RB deletion in myeloma cells of both origins. However, a P53 deletion was only detected in plasma cells from extramedullary plasmacytomas. This finding suggests that P53 deletion has a role in the lack of treatment response of extramedullary plasmacytomas.