ALBERT

Description: Background:Novel insights into the biology of myeloma cells have led to the identification of relevant prognosis factors.Cytogenetic abnormalities (CA) has become one of the most important prognostic factors, and the presence of t(4;14), t(14;16) or del(17p) are associated with poor prognosis. Although there are some reports indicating that 1q gains may be considered as a poor-risk feature, the information is not uniform. Furthermore, there are important controversies about whether or not novel agents-based combinations are able to overcome the poor prognosis of CA. In the relapse setting, the combinations including proteasome inhibitors and immunomodulatory drugs have shown to improve, and some of them to overcome, the outcome of patients with high-risk CA. Here we report a preplanned analysis, in a series of elderly newly diagnosed myeloma patients included in the Spanish GEM2010 trial and receiving VMP and Rd, in a sequential or alternating approach, in order to evaluate the influence of CA by FISH on the response rate and outcome. Patients and methods: 242 pts were randomized to receive a sequential scheme consisting of 9 cycles of VMP followed by 9 cycles of Rd or the same regimens in an alternating approach (one cycle of VMP alternating with one Rd, up to 18 cycles. VMP included the IV administration of weekly bortezomib (except in the first cycle that was given twice weekly) at 1.3 mg/m2 in combination with oral melphalan 9 mg/m2 and prednisone 60 mg/m2once daily on days 1-4. Rd treatment consisted on lenalidomide 25 mg daily on days 1-21 plus dexamethasone 40 mg weekly. FISH analysis for t(4;14), t(14;16), del(17p) and 1q gains was performed at diagnosis according to standard procedures using purified plasma cells. Results: In 174 out of the 233 patients evaluable for efficacy and safety, FISH analysis at diagnosis were available and two groups were identified: high-risk group (n= 32 patients with t(4;14) and/or t(14;16) and/or del(17p)) and standard-risk group (n=142 patients without high-risk CA). The rates of CA was similar in both treatment arms. Response Rates (RR) were no different in the high-risk vs standard-risk groups, both in the sequential (74% vs 79% RR and 42% vs 39% CR) and alternating arms (69% vs 86% RR and 39% vs 38% CR). After a median follow-up of 51 months, high-risk patients showed shorter PFS as compared to standard risk in the alternating arm (24 versus 33 months, p=0.03) and this also translated into a significantly shorter OS (38.4m vs not reached, p=0.002). However, in the sequential arm, high-risk and standard-risk patients showed similar PFS (29.5 months vs 31.5 months, p=0.9) and OS (46m vs 63m, p=0.1). This beneficial effect observed in the sequential arm applied to both t(4;14) or del(17p). As far as 1q gains is concerned, 151 patients had 1q information and 76 of them had 1q gains (50.3%), defined as the presence of more than 3 copies in at least 10% of plasma cells. The rate of 1q gains was well balanced in both sequential and alternating arms. The ORR was similar in patients with or without 1q gains (83% vs 80%) as well as the CR rate (45% vs 31%), and no differences were observed between sequential and alternating arms. Patients with or without 1q gains had a similar PFS (36 months vs 29 months) and 4-years OS (63% vs 68%) in the whole series and no differences were observed between the sequential and alternating arms. This effect has been observed in patients with 1q gains as isolated CA and the outcome was slightly but not significantly worse when 1q gains were present plus either t(4;14) and/or del17p. Conclusions: The total therapy approach including VMP and Rd administered in a sequential approach is able to overcome the poor prognosis of the presence of high-risk CA in elderly patients with newly diagnosed MM. The presence of 1q gains has no impact in the PFS and OS of elderly patients treated with VMP and Rd. Disclosures Mateos: Janssen, Celgene, Amgen, Takeda, BMS: Honoraria. Martínez-López:Novartis: Honoraria, Speakers Bureau. Oriol:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Paiva:Celgene: Honoraria, Research Funding; Janssen: Honoraria; Takeda: Honoraria, Research Funding; Sanofi: Consultancy, Research Funding; EngMab: Research Funding; Amgen: Honoraria; Binding Site: Research Funding.

Description: Introduction:SMM is an asymptomatic and heterogeneous plasma cell disorder. The Spanish Myeloma Group demonstrated that patients at high risk of progression benefit from early treatment with Rd. In addition, our preliminary results of the curative approach (GEM-CESAR) showed encouraging results (Mateos ASH 2017). Aim: The primary end-point was to evaluate the Minimal Residual Disease negative (MRD-ve) rate by next generation flow (NGF) after induction and ASCT and the sustained MRD-ve rate at 3 and 5 yrs after ASCT as secondary end-points. Our aim was to increase the MRD -ve rate from 34% (reported in NDMM patients after VTD and ASCT) to 50%. As all patients have completed induction and ASCT, we report the results of the primary end point, efficacy and safety after induction and ASCT. Methods: In this phase II single arm trial, 90 SMM patients at high-risk of progression (〉50% at 2 yrs), younger than 70 yrs 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, patients must have a proportionof aberrant PCs within the total PCsBM compartment by immunophenotypingof 95% plus immunoparesis (Spanish criteria). Asymptomatic MM patients with any of the three biomarkers recently included into the definition of active MM were allowed to be included. Induction therapy consisted on six 4-weeks cycles of KRd in which K was given at dose of 36 mg/m2twice 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/m2followed by ASCT was given as intensification therapy and three months later, patients received two KRd consolidation cycles followed by maintenance with R at dose of 10 mg on days 1-21 plus dex at dose of 20 mg weekly for up to 2 yrs Results: Between June 2015 and June 2017, the 90 SMM patients at high risk of progression were recruited. Twenty-eight pts (32%) shared at least one of the new biomarkers predicting imminent risk of progression to MM. The primary end point of the trial was met, since 55% of the patients who completed induction and ASCT achieved MRD -ve by NGF (sensitivity 3 x 10-6). Upon analyzing the results after induction, 88 patients completed the 6 induction cycles and were evaluable for response (two patients early discontinued): the ORR was 98% including 41% of ≥CR (32% sCR and 9% CR) and 41% of VGPR rate. Two patients were mobilization failures and one patient rejected ASCT. Two additional patients experienced biological progression before ASCT and went off the study. Eighty-three patients, therefore, proceeded to HDT-ASCT and were evaluable at day +100: the ORR was 100% including ≥CR in 63% of the patients (51% sCR and 12% CR) and VGPR rate in 23%. The MRD-ve rate increased from 31% after induction to 55% with the ASCT. No differences in outcome have been observed according neither to the definition of high risk (Mayo or Spanish model) nor ultra high risk SMM. Concerning toxicity, during induction, G3-4 neutropenia and thrombocytopenia were reported in 5 (6%) and 10 pts (11%), respectively. G3-4 infections were the most frequent non-hematological AE observed in 16 pts (18%), followed by skin rash in 8 pts (9%). One patient reported G1 atrial fibrillation and another cardiac failure secondary to respiratory infection. Three patients reported hypertension (G2 in two and G3 in one). Thirteen patients required lenalidomide dose reduction whilst carfilzomib was not reduced in any patient. In four patients, dexamethasone was reduced. In all but two of the pts, PBSC collection was successful with a median of 4.10 x 106/Kg CD34 cells collected. All patients engrafted. Consolidation and maintenance phases are ongoing. After a median follow-up of 17 months (5-36), 94% of patients remain alive and free of progression and 97% of them alive. Three patients experienced biological progression and discontinued the study: one of them was refractory to the rescue therapies and died and the other two are receiving rescue therapies. One additional patient died early during induction due to a massive ischemic stroke unrelated to the treatment. Conclusions: Although longer follow-up is required, this "curative strategy for high risk SMM" continues being encouraging with an acceptable toxicity profile. The study has met its primary endpoint. The depth of response improved over the treatment: 63% of patients who completed induction and ASCT achieved ≥CR with a MRD-ve rate of 55%. Disclosures Mateos: Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees. Rodriguez Otero:Takeda: Consultancy; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Bristol Myers Squibb: Research Funding; Clínica Universidad de Navarra: Employment. Ocio:AbbVie: Consultancy; Pharmamar: Consultancy; Seattle Genetics: Consultancy; Janssen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; BMS: Consultancy; Takeda: Consultancy, Honoraria; Sanofi: Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Mundipharma: Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Array Pharmaceuticals: Research Funding. Oriol:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Rios:Amgen, Celgene, Janssen, and Takeda: Consultancy. Rosinol:Janssen, Celgene, Amgen, Takeda: Honoraria. Alegre:Takeda: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees. Puig:Janssen: Consultancy, Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Takeda: Consultancy, Honoraria. De La Rubia:Ablynx: Consultancy, Other: Member of Advisory Board. García Mateo:Binding Site: Research Funding; Amgen: Honoraria; Celgene: Honoraria. Bladé:Janssen: Honoraria. Lahuerta:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. San-Miguel:Novartis: Honoraria; Janssen: Honoraria; BMS: Honoraria; Amgen: Honoraria; Celgene: Honoraria; Sanofi: Honoraria; Roche: Honoraria.

Description: Introduction: Disease control at five years would be a desirable endpoint for elderly multiple myeloma (MM) patients; however, the percentage of cases reaching this objective as well as the biomarkers to predict it, are not well defined. Objective and design: In order to gain further insight about long-term disease control (〉5 years progression-free) in elderly MM we have analyzed a homogeneous population of 435 newly-diagnosed transplant-ineligible (TNE) patients enrolled in two consecutive Spanish clinical trials (GEM2005MAS65, GEM2010MAS65), that included both proteasome inhibitors and immunomodulatory drugs. Results: Amongst the 435 patients included in this post-hoc study, only 18.8% remained alive and progression-free after five years of initiating treatment. Noteworthy, in these patients the overall survival (OS) rate at 10-years was 69.4%, as compared to 11.4% for those patients progressing during the first five years (p〈 0.001). Baseline variables significantly associated with long-term progression free survival in the univariate analysis were younger age, ISS 1, R-ISS 1, hemoglobin ≥ 12g/dl, normal LDH, and standard-risk cytogenetic abnormalities and the presence of a monoclonal gammopathy of unknown significance (MGUS)-like immunophenotypic profile in the bone marrow. Complete responses (CR) and minimal residual disease (MRD) negativity were also associated with long-term progression free survival. In the multivariate analysis, an hemoglobin level ≥12g/dl (OR 2.61; 95% CI 1.47 - 4.61, p=0.001) and a MGUS-like immunophenotypic profile in the bone marrow (OR 3.33; 95% CI 1.30 - 8.54, p=0.002) were the two baseline variables significantly and independently associated with a higher probability of long-term disease-free survival. When the depth of response (including MRD) was included in the logistic regression model, Hb level ≥12g/dl (OR 2.18; p=0.010) and the MGUS-like signature (OR 4.99, p

Description: Key Points KRd has a favorable benefit-risk profile compared with Rd, regardless of baseline cytogenetic risk status, in patients with relapsed MM. KRd improves but does not abrogate the poor prognosis associated with high-risk cytogenetics in patients with relapsed MM.

Description: Introduction: The ENDEAVOR study found that Kd was superior to Vd, with a 2-fold improvement in median PFS (18.7 vs 9.4 mo; HR=0.53; 95% CI, 0.44-0.65; P

Description: Background Bortezomib-based combinations, including alkylating agents (VMP or CyBorD) or immunomodulatory drugs (VTD or RVD) have been established as regimens widely used in newly diagnosed MM patients. Bendamustine is a bifunctional alkylating agent effective in relapsed and/or refractory MM patients, and approved in Europe in combination with prednisone for elderly newly diagnosed MM. Since bendamustine may be more efficient than other alkylators, an attractive possibility would be to explore it in combination with bortezomib and prednisone (BVP) in newly diagnosed MM patients both transplant and non transplant candidates. Patients and Methods 60 newly diagnosed MM patients were included in the trial. The first cycle consisted on bendamustine at 90 mg/m2 given IV on days 1 and 4, in combination with bortezomib at 1,3 mg/m2 given IV on days 1, 4, 8, 11, 22, 25, 29 and 32 and prednisone at 60 mg/m2 given PO on days 1 to 4. In the following cycles, bendamustine was given on days 1 and 8, and bortezomib on days 1, 8, 15 and 22 (weekly schedule), and prednisone as it was previously described. Patients younger than 65 years proceeded to peripheral blood stem cell collection (PBSC) using growth factors alone after 4 cycles; HDT-ASCT was performed after 6 cycles. Patients older than 65 years received up to nine 28-day cycles. Results Between May 2011 and July 2012 enrollment was completed (60 pts). Median age was 61 years (range 38-82; 18 pts ≥65), 67% had ISS stage II/III, and 67% had unfavorable cytogenetics: t(4;14), t(14;16), del 17p or 1q gains by FISH. After a median of 6 cycles (2-9), 75% of patients achieved at least PR, including 16% of sCR, 9% CR and 28% of VGPR. Although the differences were not statistically significant, there was a trend to higher CR rate in the group of patients

Description: Background VMP and Rd are two of the most efficient and widely accepted regimens in the treatment of elderly newly diagnosed MM patients. In order to further improve the outcome of elderly patients, one possibility would be to use regimens including all these drugs simultaneously, but this may result into high toxicity. Alternatively, the use of these regimens (VMP and Rd) in a sequential or alternating scheme could improve the treatment of elderly patients. We hypothesized the alternating scheme would minimize the emergence of resistant clones, and would reduce the cumulative toxicity. In order to test this hypothesis we decided to compare VMP and RD in a sequential vs an alternating scheme. Patients and methods 241 patients were randomized to receive a sequential scheme consisting on 9 cycles of VMP followed by 9 cycles of Rd or the same regimens in an alternating approach (one cycle of VMP alternating with one Rd (half of the patients started by VMP and half by Rd) up to 18 cycles). VMP included the iv administration of bortezomib 1.3 mg/m2 twice weekly for 1 six-weeks cycle, followed by once weekly for 8 four-weeks cycles in combination with oral melphalan 9 mg/m2 and prednisone 60 mg/m2 once daily on days 1–4 of each cycle. Rd treatment consisted on lenalidomide 25 mg daily on days 1-21 plus dexamethasone 40 mg weekly. Results 121 patients were allocated to receive the sequential scheme and 120 the alternating regimen. Both arms were well balanced according to the baseline characteristics. 52% patients in the sequential arm and 55% in the alternating and had high risk cytogenetic abnormalities (t(4;14), t(14;16), del17p or 1q gains). After 9 cycles of treatment, in the sequential arm, 35 out of 66 (54%) achieved at least VGPR vs 51 out of 65 patients (78%) in the alternating arm (p=0.002), including sCR/CR rate of 28% vs 38% in the sequential and alternating arms, respectively (p=NS). Seven patients in each arm achieved immunophenotypic CR. Moreover, while four patients progressed in the sequential arm under treatment with VMP, no patients in the alternating scheme developed disease progression during the first 9 cycles, After a median follow up of 12 months, there was a trend for shorter TTP in the sequential as compared with the alternating scheme (18 m-TTP of 83% vs 89% (p=NS)). In terms of OS, 83% of patients in the sequential arm were alive at 18 m versus 93% in the alternating (p=NS). Patients who achieved sCR/CR had a significantly longer 18 m-TTP as compared with patients who didn’t achieve it in both sequential (100% vs 71%; p=0.006) and alternating arms (100% vs 79%; p=0.006) and this translated into a significant benefit in OS. No differences were observed in overall response rates and CR rates in standard and high risk patients. The 18 m-TTP was similar in standard and high risk groups in both sequential (86% vs 81%) and alternating arms (84% vs 94%), noting that 94% of patients receiving the alternating scheme were progression-free at 18 months. Regarding hematologic toxicity, the frequency of G3-4 neutropenia was slightly lower in the sequential than in the alternating arm (16% and 23%) and the same trend was observed for G3-4 thrombocytopenia (16% vs 20%). Concerning non-hematologic toxicity, 5% and 4% of the patients in the sequential and alternating arms developed G3-4 infections, respectively; the rate of G3-4 skin rash was 4% in the sequential and 3% in the alternating arm; 4% of patients in the sequential arm developed G3-4 peripheral neuropathy and 3% in the sequential arm. The rate of grade 3-4 thrombotic events was 2% in both arms. Nevertheless, the detailed evaluation of the toxicity will be done at the completion of the trial when all patients will have received the same amount of drugs in either a sequential or an alternating scheme (at the present time, 42 patients in the sequential arm were not yet at risk for the development of lenalidomide-related side effects). Conclusions The administration of melphalan, bortezomib, lenalidomide and steroids in elderly MM patients in a sequential or alternating scheme is feasible. Although longer follow-up is necessary, the alternating scheme may be superior in terms of response rate and outcome, as result of the early exposure of the plasma cell to different agents. Toxicity profile is acceptable. Aparently both schemes of therapy seems to overcome the poor prognosis of high risk cytogenetic. Disclosures: Mateos: Janssen, Celgene: Honoraria. Off Label Use: Lenalidomide plus dexamethasone is not approved for newly diagnosed MM patients. Ocio:Onyx: Consultancy, Research Funding; Novartis: Consultancy; Array Biopharma: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy; Celgene: Consultancy, Research Funding. San Miguel:Janssen, Celgene: Membership on an entity’s Board of Directors or advisory committees.

Description: Abstract 811 Introduction: Vorinostat (VOR), an oral inhibitor of histone deacetylase class I and class II proteins, regulates genes and proteins involved in tumor growth and survival. The synergistic effects of VOR and bortezomib (BTZ) have been shown in preclinical studies and were confirmed in independent phase 1 trials in patients with relapsed/refractory multiple myeloma (MM), producing objective response rates (ORRs) of up to 42% and overall clinical benefit of up to 90%. Materials and methods: Eligible patients were aged ≥ 18 years, had measurable secretory MM, had received 1 to 3 prior systemic anti-myeloma regimens, and had an Eastern Cooperative Oncology Group status ≤ 2. Previous exposure to BTZ and the presence of extracellular plasmacytoma were allowed per protocol, but patients with prior resistance to BTZ were excluded. Patients were randomized 1:1 to receive 21-day cycles of BTZ (1.3 mg/m2 intravenously; days 1, 4, 8, and 11) in combination with oral VOR 400 mg/d, or matching placebo, on days 1 to 14. Additional use of corticosteroids for the treatment of MM was not allowed during the trial. Patients were treated until disease progression, unacceptable toxicities, or withdrawal from the study. The primary endpoint for this trial was progression-free survival (PFS; occurrence of 412 PFS events). Secondary and exploratory endpoints included ORR (≥ partial response), clinical benefit response (ORR + minimal response), overall survival, time to progression, patient-reported outcomes questionnaires (QLQ-C30, QLQ-MY20), and safety/tolerability of this novel drug combination. Responses and progression were determined according to the European Bone and Marrow Transplantation Group criteria and will be confirmed by an Independent Adjudication Committee. Results: Between January 2009 and January 2011, 637 patients were enrolled from 174 centers in 33 countries across the globe making this trial one of the largest studies conducted in patients with relapsed/refractory myeloma. Median age of the study population was 62 years (range, 29–86 years). Of the enrolled patients, 59% were male and 56% were Caucasian. Patients had received a median of 2 prior regimens (range, 1–3). Prior anti-myeloma agents included BTZ (24%), thalidomide (56%), lenalidomide (13%), melphalan (56%), and stem cell transplantation (35%). As of July 2011, 635 patients had received study medication, with a median exposure of 7 cycles (mean: 7.6 cycles; range 1–30 cycles). Reported median exposure to BTZ monotherapy in previous phase 3 trials was approximately 5 cycles. Conclusions: The study passed the protocol-specified futility analyses by the independent data monitoring committee in November 2010. Database lock is anticipated in November 2011, and top-line data on primary and secondary endpoints will be available at the meeting. Disclosures: Dimopoulos: Celgene, Ortho-Biotech: Consultancy, Honoraria. Off Label Use: Vorinostat, an inhibitor of histone deacetylase, is approved in the US for the treatment of cutaneous manifestations in patients with cutaneous T cell lymphoma (CTCL) who have progressive, persistent or recurrent disease on or following two systemic therapies. Vorinostat is currently under investigation for the treatment of relapsed malignant pleural mesothelioma, relapsed/refractory B cell lymphoma (in combination with other chemotherapy agents), and relapsed/refractory multiple myeloma (in combination with bortezomib and other chemotherapy agents). Jagannath:Merck: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees. Yoon:Celgene: Consultancy; NK Bio: Consultancy. Siegel:Millennium: Honoraria, Research Funding, Speakers Bureau; Merck: Honoraria. Lonial:Millennium: Consultancy; Celgene: Consultancy; Novartis: Consultancy; BMS: Consultancy; Onyx: Consultancy; Merck: Consultancy. Hajek:Celgene: Honoraria; Janssen: Honoraria; Merck: Educational lecture. Facon:Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Merck: Membership on an entity's Board of Directors or advisory committees. Rosiñol:Celgene: Honoraria; Janssen-Cilag: Honoraria. Blacklock:New Zealand Bone Marrow Donor Registry: Consultancy, Employment; Mercy Hospital, Auckland New Zealand: Consultancy; Leukaemia and Blood Foundation, New Zealand: Consultancy, Membership on an entity's Board of Directors or advisory committees; Middlemore Hospital: Employment, Research Funding. Goldschmidt:Amgen, Novartis, Chugai: Research Funding; Janssen-Cilag, Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Palumbo:Merck: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Janssen-Cilag: Honoraria, Membership on an entity's Board of Directors or advisory committees. Reece:Merck: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Otsuka: Honoraria, Research Funding. Graef:Merck: Employment. Houp:Merck Research Laboratories: Employment. Sun:Merck & Co., Inc.: Employment. Eid:Merck Research Laboratories: Employment. Anderson:Celgene: Consultancy; Millennium: Consultancy; Novartis: Consultancy; BMS: Consultancy; Onyx: Consultancy; Merck: Consultancy; Acetylon: founder.

Description: Patients with multiple myeloma (MM) carrying high-risk cytogenetic abnormalities (CA) have inferior outcome despite achieving similar complete response (CR) rates when compared to cases with standard-risk CA. This questions the legitimacy of CR as treatment endpoint for high-risk MM, and represents a biological conundrum regarding the nature of tumor reservoirs persisting after therapy in patients with standard- and high-risk CA. Here, we used next-generation flow (NGF) to evaluate measurable residual disease (MRD) in MM patients with standard- (N=300) vs high-risk CA (N=90) enrolled in the PETHEMA/GEM2012MENOS65 trial (NCT01916252), and to identify mechanisms determining MRD resistance in both patient subgroups (N=40). The 36-month progression-free and overall survival rates were higher than 90% in patients with undetectable MRD, with no significant differences (P≥0.202) between cases having standard- vs high-risk CA. Persistent MRD resulted in median progression-free survival of approximately three and two years in patients with standard- and high-risk CA, respectively (P