Comparable outcomes using propylene glycol-free melphalan for autologous stem cell transplantation in multiple myeloma

Autologous stem cell transplantation (ASCT) remains a mainstay in the treatment of multiple myeloma (MM). While the procedure is generally safe, toxicities associated with high-dose melphalan conditioning are common and significantly affect patient quality of life. Recently, a propylene glycol-free melphalan formulation (PG-free MEL; Evomela^®) was approved by the United States Food and Drug Administration as an ASCT conditioning regimen for MM. PG-free MEL is more soluble and stable than propylene glycol-solubilized melphalan (PG-solubilized MEL; Alkeran^®). As such, there is speculation that it could decrease toxicities and increase the efficacy of ASCT. We compared the outcomes of patients conditioned with PG-free MEL (n=216) to PG-solubilized MEL (n=200) at our institution. The baseline characteristics were similar between the two groups. After Day +0, there were no differences in terms of hospitalizations, neutropenic fevers, intravenous granisetron requirement, World Health Organization grade ≥2 oral/esophageal mucositis, intravenous fluid requirement, or narcotic requirement. However, PG-free MEL patients had a higher incidence of diarrhea, which was mostly C. difficile-negative (82% vs. 71%, P=0.015*). Day +100 hematologic responses and progression-free survival after ASCT were comparable. In summary, we demonstrate that switching to PG-free MEL did not significantly reduce short-term complications of ASCT or improve outcomes in MM.

Phase 1/2 trial of ixazomib, cyclophosphamide and dexamethasone in patients with previously untreated symptomatic multiple myeloma

Ixazomib is the first oral proteasome inhibitor to enter the clinic. Given the efficacy of bortezomib in combination with cyclophosphamide and dexamethasone, we studied the combination of ixazomib, cyclophosphamide and dexamethasone (ICd) in newly diagnosed multiple myeloma (NDMM) and patients with measurable disease, irrespective of transplant eligibility, were enrolled. The phase 1 was to determine the maximum tolerated dose (MTD) of cyclophosphamide in the combination. Patients received ixazomib 4 mg (days 1, 8, 15), dexamethasone 40 mg (days 1, 8, 15, 22), and cyclophosphamide 300 or 400 mg/m² days 1, 8, 15, 22; cycles were 28 days. We enrolled 51 patients, 10 in phase 1 and 41 patients in phase 2. The median age was 64.5 years (range: 41–88); 29% had high or intermediate risk FISH. The MTD was 400 mg/m² of cyclophosphamide weekly. The best confirmed response in all 48 patients included ≥ partial response in 77%, including ≥ VGPR in 35%; 3 patients had a sCR. The response rate for all 48 evaluable patients at 4-cycles was 71%; the median time to response was 1.9 months. Common adverse events included cytopenias, fatigue and GI intolerance. ICd is a convenient, all oral combination that is well tolerated and effective in NDMM.

Abstract 655: Hyperdiploidy in plasma cell disorders using multi-parametric flow cytometry (MFC) vs. FISH

Introduction: Hyperdiploidy on FISH portends a good prognosis in myeloma. We compared hyperdiploidy determined by MFC to that by conventional FISH.

Methods: We studied 1711 patients with plasma cell disorders who had simultaneous FISH and DNA index testing. Monotypic plasma cells in bone marrow are identified by MFC with antibodies to CD19, CD38, CD45, CD138, kappa and lambda; followed by staining by DAPI. DNA index is determined by dividing the measured DNA content of the G0/G1 abnormal plasma cells by the DNA content of the normal G0/G1 plasma cells present. Plasma cells with DNA content index of <0.95 are hypodiploid and G0/G1 DNA content index of >1.05 are considered hyperdiploid.

Results: Distribution DNA index and FISH results are described in Table 1. Sensitivity and specificity of DNA index by hyperdiploidy was 86% and 83%. Cohen's Kappa coefficient for concordance was 0.69. Sensitivity increased to 94% for those with 2 or more trisomies and 97% for 3 or more trisomies. Of the 104 patients with trisomy and non-hyperdiploid DNA index, 62% patients had monosomy (mono) or deletion (del) 13q. Overall, DNA index was lower in patients with mono 13/del 13q (1.01; 0.97-1.11) compared to those without (1.07; 1.0-1.19), p<0.001. After excluding patients with mono 13/del 13q, sensitivity and specificity of hyperdiploidy by DNA index were 92% and 82%, kappa = 0.73.

Hyperdiploidy was seen in 55% of 272 patients with newly diagnosed myeloma. Sensitivity and specificity were 88% and 93%, kappa = 0.78. After median follow-up of 2.3 yrs, those with hyperdiploid DNA index had better progression free survival at 2,3 and 5 years, 62%, 45% and 21% compared to 50%, 33% and 13% in non-hyperdiploid group, p=0.05. Median overall survival (OS) was not reached; estimated 2, 3 and 5 year OS was 83%, 76% and 63% vs. 76%, 64% and 44%, respectively; p=0.08.

Conclusions: DNA index by MFC is a rapid method to determine hyperdiploidy, with potential for replacing trisomy testing by FISH, especially when coupled with monosomy FISH probes.

Hyperdiploid N=768 n/N (%)Diploid N=762 n/N (%)Hypodiploid N=78 n/N (%)P1P2Any trisomy 619/765 (81)96/758(13)8/76 (11)<0.001<0.001One chromosome42587733191429-111362Others12204Two chromosomes8525-Three or more chromosomes492131Any translocation124/744 (17)566/748 (76)53/74 (72)<0.001<0.001t(4;14)106313t(11;14)2240127t(14;16)5325t(14;20)38-t(6;14)8104Unknown partner76524Trisomy + Translocation95/743 (13)60/744 (8)6/74 (8)0.0090.002Monosomy 13/17 or deletion 13q/17p252/759 (33)295/744 (40)54/74 (73)<0.0010.0001Monosomy 13/Deletion 13q208/717 (29)282/718 (39)20/70 (29)Monosomy 17/Deletion 17p70/749 (9)50/735 (7)20/72 (28)P1= three groups; P2= hyperdiploid vs. non-hyperdiploid

Citation Format: Surbhi Sidana, Nidhi Tandon, Dragan Jevremovic, Rhett P. Ketterling, Angela Dispenzieri, Morie A. Gertz, Francis K. Buadi, Martha Q. Lacy, William Morice, Curtis A. Hanson, Michael Timm, Patricia Greipp, Linda B. Baughn, David Dingli, Suzanne R. Hayman, Wilson I. Gonsalves, Prashant Kapoor, Robert A. Kyle, Nelson Leung, Ronald S. Go, John A. Lust, S.Vincent Rajkumar, Shaji K. Kumar. Hyperdiploidy in plasma cell disorders using multi-parametric flow cytometry (MFC) vs. FISH [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 655.

Time to plateau as a predictor of survival in newly diagnosed multiple myeloma

Response rates in newly diagnosed multiple myeloma have improved dramatically with the introduction of highly effective novel therapies. However, survival in patients achieving optimal responses to initial treatment can vary significantly, and new prognostic indicators are required to improve risk stratification. We investigated the relationship between time to plateau (T_Plat ) and survival in 1099 newly diagnosed patients treated with novel agents at our institution from 2005 to 2015. T_Plat was defined as time from initiation of first-line therapy to best response to first-line therapy. The median T_Plat was 4.9 months (0.7-58.6) and plateau duration was 1.8 years (0.2-11.0). Patients who required > 120 days to achieve a plateau had longer modified overall survival (mOS) and progression free survival (mPFS) calculated from a landmark of best response (P < .001 for both comparisons). Statistically significant improvement in mOS was retained in subgroup analysis based on age and whether patients received upfront autologous hematopoietic stem cell transplantation (ASCT) (P < .001 for all comparisons). Our results suggest that patients who respond more gradually to initial therapy (T_Plat  > 120 days) experience longer survival compared to more rapid responders. Patients with a prolonged T_Plat could represent an "ongoing responder" phenotype that portends a survival advantage independent of treatment with upfront ASCT, depth of response, and biologic markers such as ISS stage and cytogenetic risk.

Risk stratification of smoldering multiple myeloma incorporating revised IMWG diagnostic criteria

In 2014, the International Myeloma Working Group reclassified patients with smoldering multiple myeloma (SMM) and bone marrow-plasma cell percentage (BMPC%) ≥ 60%, or serum free light chain ratio (FLCr) ≥ 100 or >1 focal lesion on magnetic resonance imaging as multiple myeloma (MM). Predictors of progression in patients currently classified as SMM are not known. We identified 421 patients with SMM, diagnosed between 2003 and 2015. The median time to progression (TTP) was 57 months (CI, 45–72). BMPC% > 20% [hazard ratio (HR): 2.28 (CI, 1.63–3.20); p < 0.0001]; M-protein > 2g/dL [HR: 1.56 (CI, 1.11–2.20); p = 0.01], and FLCr > 20 [HR: 2.13 (CI, 1.55–2.93); p < 0.0001] independently predicted shorter TTP in multivariate analysis. Age and immunoparesis were not significant. We stratified patients into three groups: low risk (none of the three risk factors; n = 143); intermediate risk (one of the three risk factors; n = 121); and high risk (≥2 of the three risk factors; n = 153). The median TTP for low-, intermediate-, and high-risk groups were 110, 68, and 29 months, respectively (p < 0.0001). BMPC% > 20%, M-protein > 2 g/dL, and FLCr > 20 at diagnosis can be used to risk stratify patients with SMM. Patients with high-risk SMM need close follow-up and are candidates for clinical trials aiming to prevent progression.

Digoxin use in systemic light-chain (AL) amyloidosis: contra-indicated or cautious use?

AIM

Digoxin is considered contraindicated in light-chain (AL) amyloidosis, given reports of increased toxicity published 30-50 years ago. We sought to determine the frequency of digoxin toxicity in patients with AL.

METHODS

We identified 107 patients with AL amyloidosis who received digoxin between 2000 and 2015.

RESULTS

The median age was 65 and the median digoxin dose and estimated glomerular filtration rate were 0.125 mg/d and 55 ml/min/1.73 m², respectively. Digoxin dose was reduced in 16% of the patients, mainly due to high serum drug concentration or worsening renal function. The median duration of therapy was 5 months, with half of the patients stopping treatment, primarily due to physician preference. Significant arrhythmias developed in 11% of patients, almost exclusively in newly diagnosed patients. Arrhythmias presented as terminal events in five patients; four with bradycardia followed by pulseless electrical activity (PEA) with ventricular tachycardia/fibrillation (VT/VF) during resuscitation; all patients had acute renal failure and severe, decompensated heart failure. One patient had ventricular tachycardia as a terminal event. Only one patient was treated with digoxin antibody therapy.

CONCLUSIONS

Digoxin may be cautiously utilized in AL amyloidosis patients. We suggest its use in lower doses and frequent drug concentration monitoring along with close monitoring of electrolytes and renal function. Nonetheless, toxicity at low serum concentration cannot be excluded due to potential for toxic concentration at the tissue level and should be taken under consideration when prescribing digoxin for these patients. Studies with higher-level evidence are needed to confirm these findings.

Efficacy of VDT PACE-like regimens in treatment of relapsed/refractory multiple myeloma

Experience with intensive chemotherapy for relapsed/refractory multiple myeloma (RRMM) using VDT PACE regimen and its modifications (VDT PACE-like regimens: VPLRs) outside TOTAL THERAPY trials is limited. We analyzed the outcomes of 141 patients with RRMM who received VPLRs at our center between 2006 and 2017 in an intent-to-treat analysis. Median age was 59.7 years and 66.7% of patients were male. A median of 2.2 years (range 0.02-11.4) separated diagnosis of myeloma and inititation of VPLR. High-risk cytogenetics were present in 52.4% patients. Patients received a median of 4 (range 1-14) prior therapies, including stem cell transplant (SCT) in 66.7% patients. Ninety-five (67.4%) patients received VDT PACE, 20 (14.2%) patients received VD PACE and 26 (18.4%) patients received other VPLRs. Patients received a median of 1 cycle (range 1-9) of VPLR. We observed ≥ minimal response in 68.4%, ≥ partial response (PR) in 54.4% and ≥ very good PR in 10.3% patients. Median progression-free survival was 3.1 months (95% CI, 1.9-3.9) and median overall survival (OS) was 8.1 months (CI, 6.2-9.9). One-hundred and sixteen (82.3%) patients received some therapy after VPLR; 71 (61.2%) received systemic chemotherapy, while 45 (38.8%) underwent SCT. Median OS for those who received SCT after VPLR was 15.1 months (CI, 10.3-20.8). Age ≥ 60 years (hazard ratio [HR] 2.3 [CI, 1.4-3.7]; P = 0.0008) and R-ISS III stage (HR- 2.4 [CI, 1.3-4.0]; P = 0.003) predicted shorter OS in patients receiving VPLR. VPLRs are effective in heavily pre-treated RRMM. In fit patients, SCT can be used to consolidate the response to VPLR.

MYD88 mutation status does not impact overall survival in Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is an immunoglobulin M-associated lymphoma, with majority of cases demonstrating MYD88 locus alteration, most commonly, MYD88^L265P . Owing to low prevalence of the wild-type (WT) MYD88 genotype in WM, clinically relevant data in this patient population are sparse, with one study showing nearly a 10-fold increased risk of mortality in this subgroup compared to patients with MYD88^L265P mutation. We studied a large cohort of patients with MYD88^L265P and MYD88^WT WM, evaluated at Mayo Clinic, Rochester, between 1995 and 2016, to specifically assess the impact of these genotypes on clinical course. Of 557 patients, MYD88^L265P mutation status, as determined by allele-specific polymerase chain reaction, was known in 219, and 174 (79%) of those exhibited MYD88^L265P , 157 of 174 patients had active disease. Of 45 (21%) patients with MYD88^WT genotype, 44 had active disease. The estimated median follow-up was 7.0 years; median overall survival was 10.2 years (95% CI: 8.4-16.5) for MYD88^L265P versus 13.9 years (95% CI: 6.4-29.3) for the MYD88^WT (P = 0.86). The time-to-next therapy from frontline treatment and the presenting features were similar in the two patient populations. For patients with smoldering WM at diagnosis, the median time-to-progression to active disease was 2.8 years (95% CI: 2.2-3.8) in the MYD88^L265P cohort and 1.9 years (95% CI: 0.7-3.1) in the MYD88^WT cohort (P = 0.21). The frequency of transformation to high-grade lymphoma, or the development of therapy-elated myelodysplastic syndrome was higher in the MYD88^WT cohort (16% versus 4% in the MYD88^L265P , P = 0.009). In conclusion, MYD88^L265P mutation does not appear to be a determinant of outcome, and its presence may not be a disease-defining feature in WM. Our findings warrant external validation, preferably through prospective studies.

Safety Outcomes for Autologous Stem Cell Transplant in Multiple Myeloma

Systems have been put in place in the Mayo Clinic Stem Cell Transplantation program to reduce day-100 all-cause mortality. Currently our mortality has been reduced to 0.3%. Patients can undergo transplant as an outpatient, with a median hospital duration of 0 days and only 25% of patients requiring a hospital stay of 5 days or greater. Outpatient transplantation is safe and reduces patient-incurred costs.

Impact of involved free light chain (FLC) levels in patients achieving normal FLC ratio after initial therapy in light chain amyloidosis (AL)

Achievement of a normal FLC ratio (FLCr) following treatment indicates hematologic response and suggests better outcomes in light chain amyloidosis (AL). We examined if elevated involved free light chain (hiFLC) impacts outcomes in patients achieving normal FLCr. We retrospectively analyzed 345 AL patients who were diagnosed within a 10-year period (2006-2015) and had 2 consecutive normal FLCr values after 1st line treatment. Among these, patients with hiFLC at 1^st reading of normal FLCr (hiFLC1; n = 166; 48.1%) were compared to those who did not (n = 179; 51.9%). Patients with AL who have hiFLC1 after initial therapy had higher rates of multi-organ involvement (63.3 vs 46.4%; P = .002) and patients in advanced Mayo stage (42.9 vs 32.2%; P = .04) at diagnosis. The median progression free survival [PFS; 38.2 (95%CI; 26.4, 55.4) vs 67.1 (95%CI; 55.8, 88) months; P = .0002] and overall survival [OS; 94.4 (95%CI; 78, 107.1) vs not reached (NR, 95%CI; 116.1, NR) months; P < .0001] were lower in those who had hiFLC1. A more stringent comparison for patients with 2 consecutive hiFLC (hIFLC2; n = 111; 32.2%) versus not (n = 2234; 67.8%) showed consistent results [PFS; 27.1 (95%CI; 23, 53.8) vs 63.3 (95%CI; 55.4, 77) months; P < .0001 and OS; 78 (95% CI; 54.6, 98.8) vs NR (95%CI; NR, NR); P < .0001]. This poor prognostic impact of hiFLC on survival was independent of serum creatinine, Mayo stage, negative immunofixation status and inclusion of transplant in initial therapy on multivariate analysis. Hence, persistent elevation of iFLC predicts poor prognosis even among patients achieving normal ratio after initial therapy in AL.

Elevated pre-transplant C-reactive protein identifies a high-risk subgroup in multiple myeloma patients undergoing delayed autologous stem cell transplantation

The significance of elevated C-reactive protein (CRP) prior to autologous stem cell transplantation (ASCT) in multiple myeloma (MM) has not been studied. We analyzed 1111 MM patients who underwent ASCT at Mayo Clinic from 2007 to 2015. A total of 840 patients (76%) received early ASCT (⩽12 months from diagnosis) and 271 patients (24%) received delayed ASCT (>12 months from diagnosis). Elevated CRP (> upper normal limit (8 mg/L)) was seen in 14% and 22% of patients undergoing early and delayed ASCT, respectively (P=0.003). There was no correlation of CRP with pre-transplant response, bone marrow plasma cell percentage or labeling index. Patients with an elevated CRP had a higher likelihood of having circulating plasma cells prior to ASCT (33 vs 19%; P<0.001). In the early ASCT cohort, the median overall survival (OS) in patients with normal and elevated CRP was not reached and 91 months respectively (P=0.011). In the delayed ASCT cohort, the median OS in respective groups were 73 and 30 months respectively (P<0.001), with elevated CRP being an independent prognostic marker on multivariate analysis (hazard ratio 2.0; 95% confidence interval, 1.0-3.8; P=0.045). Elevated pre-transplant CRP identifies a high-risk population especially in patients undergoing delayed ASCT and should be incorporated in the pre-transplant evaluation.

Efficacy of daratumumab-based therapies in patients with relapsed, refractory multiple myeloma treated outside of clinical trials

Outside of clinical trials, experience with daratumumab-based combination therapies (DCTs) using bortezomib (V)/lenalidomide (R)/pomalidomide (P), and dexamethasone (d) in relapsed/refractory multiple myeloma (RRMM) is limited. We reviewed the outcomes of 126 patients who received ≥ 1 cycle of any DCT. Median age at DCT initiation was 67 (range, 43-93) years. High-risk cytogenetics was present in 33% patients. Median number of prior therapies was 4 (range, 1-14) and time to first DCT from diagnosis was 4.3 years (range, 0.4-13.0). Seventeen (13%) patients were refractory to single agent daratumumab. Fifty-two (41%), 34 (27%), 23 (18%), and 17 (14%) received DPd, DRd, DVd and "other" DCTs, respectively. Overall response rate was 47%. Median follow-up was 5.5 months (95% CI, 4.2-6.1). Median progression-free survival (PFS) was 5.5 months (95% CI, 4.2-7.8). Median overall survival was not reached (NR) with any regimen. Median PFS (months) was worst for penta-refractory MM (n = 8) vs quadruple refractory MM (n = 18) and others (n = 100) (2.2 [95% CI, 1-2.4] vs 3.1 [95% CI, 2.1-NR] vs 5.9 [95% CI, 5.0-NR]; P < .001); those who were refractory to ≥1 agents used in the DCT vs others (4.9 [95% CI, 3.1-6.0] vs 8.2 [95% CI, 4.6-NR]; P = .02); and those who received >2 prior therapies vs others (5.0 months [95% CI, 3.7-5.9] vs NR [95% CI, NR-NR]; P = .002). Non-hematologic toxicities included infections (38%), fatigue (32%), and infusion reactions (18%). Grade 3 or higher hematological toxicities were seen in 41% of patients. DCTs are effective in RRMM. ORR and PFS in heavily pretreated patients are lower than those reported in clinical trials.

Overuse of organ biopsies in immunoglobulin light chain amyloidosis (AL): the consequence of failure of early recognition

INTRODUCTION

The diagnosis of amyloidosis requires histological confirmation of Congo-red (CR) deposits. The tissue source is preferably fat aspiration and/or bone marrow (BM) biopsy, but at times organ biopsy is required.

METHODS

We studied 612 patients with systemic immunoglobulin light chain amyloidosis to characterise the tissues used to establish the diagnosis.

RESULTS

The median number of tissue samples was 3. About 95% of BM biopsies were stained for CR, while 79% of patients had fat aspiration CR-stained. CR stain sensitivity was 69% in BM, 75% in fat aspiration and 89% for both sources combined. In comparison, CR sensitivity was 97-100% for heart, renal and liver biopsies. About 42% of patients with renal involvement, 21% of patients with liver involvement and 13% of patients with heart involvement underwent organ biopsy, when a less invasive biopsy would have established the diagnosis. Predictors for the requirement for organ biopsy were male sex, limited organ involvement and lack of fat aspiration.

DISCUSSION

Fat aspiration is underutilised for histologic confirmation of amyloidosis. A high rate of organ biopsies represents a failure to recognise the disease. Early awareness of amyloidosis in patients with organ dysfunction may lead to more judicious use of organ biopsies in this disease. Key messages Fat pad aspiration is underutilised to establish the diagnosis of amyloidosis. Bone marrow and fat pad aspiration obviates the need for invasive biopsies. The excessive use of organ biopsy in AL amyloidosis reflects failure to recognise the disease early in its course.

Diagnosis and Management of Waldenström Macroglobulinemia: Mayo Stratification of Macroglobulinemia and Risk-Adapted Therapy (mSMART) Guidelines 2016

Importance

Waldenström macroglobulinemia (WM), an IgM-associated lymphoplasmacytic lymphoma, has witnessed several practice-altering advances in recent years. With availability of a wider array of therapies, the management strategies have become increasingly complex. Our multidisciplinary team appraised studies published or presented up to December 2015 to provide consensus recommendations for a risk-adapted approach to WM, using a grading system.

Observations

Waldenström macroglobulinemia remains a rare, incurable cancer, with a heterogeneous disease course. The major classes of effective agents in WM include monoclonal antibodies, alkylating agents, purine analogs, proteasome inhibitors, immunomodulatory drugs, and mammalian target of rapamycin inhibitors. However, the highest-quality evidence from rigorously conducted randomized clinical trials remains scant.

Conclusions and Relevance

Recognizing the paucity of data, we advocate participation in clinical trials, if available, at every stage of WM. Specific indications exist for initiation of therapy. Outside clinical trials, based on the synthesis of available evidence, we recommend bendamustine-rituximab as primary therapy for bulky disease, profound hematologic compromise, or constitutional symptoms attributable to WM. Dexamethasone-rituximab-cyclophosphamide is an alternative, particularly for nonbulky WM. Routine rituximab maintenance should be avoided. Plasma exchange should be promptly initiated before cytoreduction for hyperviscosity-related symptoms. Stem cell harvest for future use may be considered in first remission for patients 70 years or younger who are potential candidates for autologous stem cell transplantation. At relapse, retreatment with the original therapy is reasonable in patients with prior durable responses (time to next therapy ≥3 years) and good tolerability to previous regimen. Ibrutinib is efficacious in patients with relapsed or refractory disease harboring MYD88 L265P mutation. In the absence of neuropathy, a bortezomib-rituximab-based option is reasonable for relapsed or refractory disease. In select patients with chemosensitive disease, autologous stem cell transplantation should be considered at first or second relapse. Everolimus and purine analogs are suitable options for refractory or multiply relapsed WM. Our recommendations are periodically updated as new, clinically relevant information emerges.

Pomalidomide, bortezomib, and dexamethasone for patients with relapsed lenalidomide-refractory multiple myeloma

This phase 1/2 trial evaluated the maximum tolerated doses, safety, and efficacy of pomalidomide, bortezomib, and dexamethasone (PVD) combination in patients with relapsed lenalidomide-refractory multiple myeloma (MM). In phase 1, dose level 1 consisted of pomalidomide (4 mg by mouth on days 1 to 21), IV or subcutaneous bortezomib (1.0 mg/m2 on days 1, 8, 15, and 22), and dexamethasone (40 mg by mouth on days 1, 8, 15, and 22) given every 28 days. Bortezomib was increased to 1.3 mg/m2 for dose level 2 and adopted in the phase 2 expansion cohort. We describe the results of 50 patients. Objective response rate was 86% (95% confidence interval [CI], 73-94) among all evaluable patients (stringent complete response, 12%; complete response, 10%; very good partial response, 28%; and partial response, 36%) and 100% among high-risk patients. Within a median follow-up of 42 months, 20% remain progression free, 66% are alive, and 4% remain on treatment. Median progression-free survival was 13.7 months (95% CI, 9.6-17.7). The most common toxicities were neutropenia (96%), leukopenia (84%), thrombocytopenia (82%), anemia (74%), and fatigue (72%); however, the majority of these were grade 1 or 2. The most common grade ≥3 toxicities included neutropenia (70%), leukopenia (36%), and lymphopenia (20%). Deep vein thrombosis occurred in 5 patients. In conclusion, PVD is a highly effective combination in lenalidomide-refractory MM patients. Weekly administration of bortezomib enhanced tolerability and convenience. Toxicities are manageable, mostly consisting of mild cytopenias with no significant neuropathy. This trial was registered at www.clinicaltrials.gov as #NCT01212952.