Current approaches for the treatment of multiple myeloma
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- Watanabe, R., Tokuhira, M. & Kizaki, M. Int J Hematol (2013) 97: 333. doi:10.1007/s12185-013-1294-z
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The development of novel therapeutic agents over the past decade, including the proteasome inhibitor, bortezomib, and the immunomodulatory drugs, lenalidomide and thalidomide, has resulted in improved outcomes for patients with multiple myeloma. However, there is still considerable controversy as to which regimen should be used as first-line therapy, which patients should be considered for autologous or allogeneic transplantation, and how consolidation or maintenance therapy is used in patients that have a good response to first-line therapy. The present paper will review clinical evidence from previous and ongoing studies to explore issues related to these questions.
KeywordsMultiple myelomaBortezomibLenalidomideThalidomideStem cell transplantation
NCCN guidelines version l. 2013 multiple myeloma
Primary therapy for transplant candidates (assessed for response after 2 cycles)
BOR/DEX (category 1)
BOR/doxorubicin/DEX (category 1)
BOR/THAL/DEX (category 1)
LEN/DEX (category 1)
DEX (category 2B)
Liposomal doxorubicin/vincristine/DEX (DVD) (category 2B)
THAL/DEX (category 2B)
Primary therapy for non-transplant candidates (assessed for response after 2 cycles)
LEN/low-dose DEX (category 1)
MEL/prednisone/BOR (MPB) (category 1)
MEL/prednisone/LEN (MPL) (category 1)
MEL/prednisone/THAL (MPT) (category 1)
DEX (category 2B)
Liposomal doxorubicin/vincristine/DEX (DVD) (category 2B)
THAL/DEX (category 2B)
Vincristine/doxorubicin/dexamethasone (VAD) (category 2B)
LEN (category 1)
THAL (category 1)
Interferon (category 2B)
Steroids (category 2B)
THAL/prednisone (category 2B)
Repeat primary induction therapy (if relapse at > 6 months)
BOR (category 1)
BOR/DEX (category 1)
BOR/liposomal doxorubicin (category 1)
DEX/THAL/cisplatin/doxorubicin/Cy (DT-PACE) ± BOR (VTD-PACE)
LEN/DEX (category 1)
Induction therapy in patients eligible for autologous stem cell transplantation (ASCT)
Phase III trials for patients eligible for autologous transplantation
≥VGPR (CR) after induction
≥VGPR (CR) after ASCT
IFM 2005-01 Harousseau et al. 
BD (Dex or DCEP maintenance)
38 % (15 %)
54 % (35 %)
81 % at 3 years
VAD (DCEP maintenance)
15 % (6 %) (+nCR)
37 % (18 %) (+nCR)
77 % at 3 years
HOVON-65/GMMG-HD4 Sonneveld et al. 
PAD (BOR maintenance)
42 % (11 %)
61 % (30 %)
46 % at 3 years
78 % at 3 years
VAD (THAL maintenance)
15 % (5 %) (+nCR)
36 % (15 %) (+nCR)
42 % at 3 years
70 % at 3 years
GIMEMA MMY-3006 Cavo et al. 
VTD (VTD maintenance)
62 % (19 %)
82 % (42 %)
68 % at 3 years
86 % at 3 years
TD (TD maintenance)
28 % (5 %)
64 % (30 %)
56 % at 3 years
84 % at 3 years
PETHEMA/GEM Rosiñol et al. 
VTD (LEN maintenance)
60 % (35 %)
74 % at 4 years
29 % (14 %)
65 % at 4 years
36 % (21 %)
70 % at 4 years
IFM2007-02 Moreau et al. 
49 % (13 %)
74 % (31 %)
36 % (12 %)
58 % (29 %)
SWOG S0232 Zonder et al. 
ECOG E4A03 Rajkumar et al. 
50 % (5 %)
40 % (4 %)
HOVON50 Lokhorst et al. 
TAD (THAL maintenance)
37 % (3 %)
54 % (14 %)
VAD (IFN maintenance)
18 % (2 %)
44 % (12 %)
MRC IX Morgan et al. 
43 % (13 %)
74 % (50 %)
27 % (8 %)
62 % (50 %)
BOR is widely recognized as a basic agent in first-line therapy. BOR can be used in patients with renal failure, but its association with herpes zoster infection means that low-dose acyclovir should be used for prophylaxis in patients being treated with this agent.
BOR-based two- or three-drug combination regimens
In the phase III Intergroupe Franco du Myelome (IFM) 2005–2001 trial (n = 482) , BOR plus dexamethasone (BD) was compared with VAD. Overall response rates (ORR, 78.5 % in the BD arm vs. 62.8 % in the VAD arm), and rates of complete remission (CR), near CR (nCR), and very good partial response (VGPR) were significantly better in the BD arm when compared with standard chemotherapy. Of note, BD was effective in high-risk patients with International Staging System (ISS) III disease and cytogenetic abnormalities, such as 13-del. The BD arm was associated with lower hematological toxicity and higher incidences of >grade 2/3 peripheral neuropathy (PN) (29.7 % in BD vs. 13 % in VAD) when compared with the VAD arm. The HOVON/GMMG-HD4 trial  reported high ORR after induction therapy with BOR, doxorubicin and DEX (PAD) when compared with VAD. A significantly higher response rate was obtained in the PAD arm, and this advantage was maintained with superior ORR after ASCT. The incidence of grade 3/4 PN was higher with BOR than with VAD (16 vs. 7 %). A phase II study has demonstrated a rapid and profound response to cyclophosphamide (Cy), BOR, DEX (CyBorD)  in patients with newly diagnosed MM (n = 33). In response to this regimen, the ORR was 88 %, a response ≥VGPR occurred in 76 %, and CR/nCR occurred in 39 %. In the 23 patients that underwent ASCT and were evaluable at day 100, CR/nCR occurred in 70 %.
BOR + THAL regimen
The Italian Multiple Myeloma Network conducted the GIMEMA trial , which investigated the efficacy of BOR–THAL–DEX (VTD) versus THAL–DEX (TD). These conditioning regimens were followed by tandem ASCT and maintenance with the same regimen. ORR and progression-free survival (PFS) were significantly better in the VTD arm, although 3-year overall survival (OS) was similar when comparing the two arms. Grade 3/4 adverse events were more common with VTD than with TD (56 vs. 33 %). The incidence of PN was particularly high with VTD when compared with TD (10 vs. 2 %).
The Spanish Myeloma Group (PETHEMA/GEM)  compared VTD versus TD, versus alternating combination chemotherapy vincristine, carmustine (BCNU), melphalan, cyclophosphamide, prednisone (VBMCP)/vincristine, BCNU, doxorubicin, dexamethasone (VBAD) followed by bortezomib (VBMCP/VBAD/B). Pre- and post-ASCT CR rates were significantly higher with VTD than with TD or with VBMCP/VBAD/B. The IFM  studied the efficacy of reduced-dose BOR–THAL–DEX (vtD) versus BD. After four cycles, the CR rate was the same in both groups (13 vs. 12 %). However, the VGPR plus CR rate was higher in the vtD arm when compared with the BD arm (49 vs. 36 %). Of note, the VGPR plus CR rate after ASCT was significantly higher in the vtD arm when compared with the BD arm (74 vs. 58 %), and the incidence of grade 3/4 PN was lower with vtD than with BD (14 vs. 34 %).
LEN is a promising agent for use in induction therapy regimens and also in regimens for relapsed or refractory patients. The Southwest Oncology Group (SWOG)  S0232 study was conducted to compare LEN–DEX (LD) with high-dose DEX in patients with newly diagnosed MM. In this study, crossover to another arm was encouraged on progression. At interim analysis, many patients in the DEX arm (n = 42) crossed over to the LD arm. At the time, a preliminary report from the Eastern Cooperative Oncology Group (ECOG) phase III study (E4A03)  suggested that 1-year survival was significantly better in the LEN plus low-dose DEX (Ld) arm when compared with the LEN plus high-dose DEX (LD) arm, and this SWOG study closed early. The SWOG study  reported that PFS (78 vs. 52 %), ORR (78 vs. 48 %) and VGPR (63 vs. 16 %) were significantly better with LD than with DEX, but that 1-year OS was similar when comparing the two arms. Toxicity ≥grade 3, including neutropenia (21 vs. 5 %) and deep vein thrombosis (DVT) (23.5 vs. 5 %), occurred more commonly in the LD arm than in the DEX arm.
The ECOG E4A03 study  was conducted to compare LD versus Ld. Of note, 79 % of the LD arm and 68 % of the Ld arm had CR or PR within four cycles. However, at interim analysis at 1 year, OS was 96 % in the Ld arm and 87 % in the LD arm (p = 0.0002). As a result, this clinical trial was discontinued, and patients in LD arm were crossed over to the Ld arm because of serious adverse effects in the LD arm. Toxic effects ≥grade 3 in during the first 4 months were more frequently observed in the LD arm than in the Ld arm, including DVT (26 vs. 12 %), infection (16 vs. 9 %), and general fatigue (15 vs. 9 %). Ld was also associated with better short-term OS and lower toxicity when compared with LD.
When using LEN in the early phase of MM treatment, clinicians should keep in mind that stem cells must be collected during the four courses of LEN, because a decrease in CD34-positive cells collected after prolonged LEN treatment has been reported .
BOR plus LEN regimen
The combination of BOR, LEN, and DEX (VRD) as primary therapy was evaluated in a phase 1/2 study . This regimen was associated with a high response rate (VGPR or better) of 74 %. Toxicities included sensory neuropathy (80 %) and fatigue (64 %), with ≥grade 3 neuropathy occurring in 2 % and ≥grade 3 fatigue occurring in 3 %. Thrombosis was rare (6 % overall). With a median follow-up of 21 months, the rate of 18-month PFS and 18-month OS was 75 and 97 %, respectively.
The randomized phase II EVOLUTION trial (n = 140)  evaluated the tolerability and efficacy of three- or four-drug regimens, including BOR, DEX, Cy, LEN (VDCR); BOR, DEX, LEN (VDR); BOR and DEX with Cy (VDC) or reduced Cy (VDC-mod). The ORR of the VDR arm after primary therapy followed by maintenance therapy with BOR was 85 %, with a CR occurring in 24 %. There was no substantial advantage with four-drug regimens when compared with three-drug regimens.
HDT + ASCT in the era of novel agents
Since the mid 1990s, HDT followed by ASCT has been considered the standard care for the frontline therapy in younger MM patients. Seven randomized trials investigated the efficacy of conventional chemotherapy (CCT) versus HDT + ASCT . In all of them, the response rate was higher in the ASCT arm when compared with the CCT arm. In six of seven trials, event-free survival (EFS) was better for the ASCT arm when compared with the CCT arm. In three of seven trials, OS was better for the ASCT arm when compared with the CCT arm. One intent-to-treat trial compared early versus late ASCT  by randomizing 185 patients to receive ASCT (early ASCT) or a conventional dose chemotherapy regimen (late ASCT). In the latter group, ASCT was performed as rescue treatment. Although the estimated median survival was similar (64.6 months in early ASCT vs. 64 months in late ASCT), average time without symptoms, treatment, and treatment toxicity was 27.8 months in early ASCT versus 22.3 months in late ASCT. These data suggest that early ASCT is associated with better quality of life when compared with late ASCT.
Evaluation of the long-term prognostic significance of the response after ASCT was reported at a median follow-up of 153 months in 344 patients who underwent ASCT . Achieving CR after ASCT is an important prognostic factor, and one landmark study showed a plateau phase in OS after 11 years; 35 % patients in the CR group and 11 % in the nCR + VGPR + PR group were alive at 17 years.
Over the past decade, the novel agents, BOR, LEN, and THAL, have been incorporated into frontline therapy for patients with MM. When compared with previously used chemotherapeutic agents, a higher CR rate and longer PFS has been achieved with novel agents containing frontline regimen. Therefore, the role of HDC + ASCT remains a matter of debate [21–24]: should all eligible patients with MM receive up front ASCT as a part of initial treatment or should ASCT be preserved as a salvage treatment for use at the time of progression of MM in patients initially treated with novel agents? Two large ongoing phase III studies are investigating the efficacy of up front HDC + ASCT. The first study is being conducted by the European Myeloma Network and is comparing VMP induction with high-dose melphalan and ASCT followed by VRD consolidation and LEN maintenance in patients with newly diagnosed MM. The second study is the Dana-Farber Cancer Institute (DFCI) 10-106 trial, which is a randomized trial of LEN, BOR, DEX versus HDT with SCT in patients younger than 65 years. Indications for ASCT may change based on the results of these studies.
Tandem ASCT refers to a planned second ASCT within 6 months after the first ASCT. According to the NCCN MM panel, a tandem transplant should be considered for all patients who are candidates for SCT and is an option for patients who do not achieve at least a VGPR after first ASCT . The JSM also recommends peripheral stem cell collection in the early phase of treatment in case tandem ASCT is indicated .
Patients ineligible for HDT + ASCT
Phase III trials for patients ineligible for autologous transplantation
71 % (30 %)
46 % at 5 years
35 % (4 %)
34.4 % at 5 years
Niesvizky et al. 
VD (BOR maintenance)
71 % (31 %)a
VTD (BOR maintenance)
79 % (38 %)a
VMP (BOR maintenance)
73 % (34 %)a
Mateos et al. 
VMP (VT or VP maintenance)
81 % (20 %)
74 % at 3 years
VTP (VT or VP maintenance)
79 % (27 %)
65 % at 3 years
Palumbo et al. 
42 % (2 %)
85 % at 3 years
BMPT (VT maintenance)
37 % (2 %)
80 % at 3 years
Lenalidomide-based regimens Rajkumar et al. 
81 % (5 %)
67 % at 2 yearsc
70 % (4 %)
82 % at 2 yearsc
MM-015 Palumbo et al. 
MPR-R (LEN maintenance)
77 % (16 %)
67 % (13 %)
50 % (4 %)
Thalidomide-based regimens GIMEMA Palumbo et al. 
MPT (THAL maintenance)
76 % (16 %)
48 % (4 %)
IFM 99-06 Facon et al. 
76 % (13 %)
35 % (2 %)
IFM 01/01 Hulin et al. 
62 % (7 %)
31 % (1 %)
HOVON49 Wijermans et al. 
MPT (THAL maintenance)
66 % (NA)
45 % (NA)
NMSG Waage et al. 
MPT (THAL maintenance)
57 % (13 %)
40 % (4 %)
TMSG Beksac et al. 
58 % (9 %)
38 % (9 %)
Ludwig et al. 
42 % (2 %)
37 % (2 %)
MRC Myeloma IX Morgan et al. 
64 % (13 %)
33 % (2 %)
Suggested age-adjusted dose reduction in patients with multiple myeloma
Age < 65 years
Age 65–75 years
Age > 75 years
Dose of 40 mg/day given orally on days 1–4, 15–18 every 4 weeks; or 40 mg/day given orally on days 1, 8, 15, 22 every 4 weeks
Dose of 40 mg/day given orally on days 1, 8, 15, 22 every 4 weeks
Dose of 20 mg/day given orally on days 1, 8, 15, 22 every 4 weeks
Dose of 0.25 mg/kg given orally on days 1–4 every 6 weeks
Dose of 0.25 mg/kg given orally on days 1–4 every 6 weeks; or 0.18 mg/kg given orally on days 1–4 every 4 weeks
Dose of 0.18 mg/kg given orally on days 1–4 every 6 weeks; or 0.13 mg/kg given orally on days 1–4 every 4 weeks
Dose of 300 mg/m2 given orally on days 1, 8, 15, 22 every 4 weeks
Dose of 300 mg/m2 given orally on days 1, 8, 15, 22 every 4 weeks, or 50 mg/day given orally on days 1–21 every 4 weeks
Dose of 50 mg/m2 given orally on days 1–21 every 4 weeks; or 50 mg/day every other day given orally on days 1–21 every 4 weeks
Dose of 200 mg/day given orally continuously
Dose of 100 or 200 mg/day given orally continuously
Dose of 50–100 mg/day given orally continuously
Dose of 25 mg/day given orally on days 1–21 every 4 weeks
Dose of 15–25 mg/day given orally on days 1–21 every 4 weeks
Dose of 10–25 mg/day given orally on days 1–21 every 4 weeks
Dose of 1.3 mg/m2 given as bolus intravenous infusion on days 1, 4, 8, 11 every 3 weeks
Dose of 1.3 mg/m2 given as bolus intravenous infusion on days 1, 4, 8, 11 every 3 weeks; or 1.3 mg/m2 given bolus intravenous infusion on days 1, 8, 15, 22 every 5 weeks
Dose of 1.0–1.3 mg/m2 given as bolus intravenous infusion on days 1, 8, 15, 22 every 5 weeks
The combination of BOR and MP (VMP) versus MP was investigated in the large international phase III VISTA (BOR as initial standard therapy in MM) trial (n = 682) [25–27]. VMP was significantly superior to MP in terms of PR (71 vs. 35 %), CR (30 vs. 4 %), PFS (24 vs. 16 months) and OS. In fact, the 3-year OS rate was 68.5 % in the VMP arm when compared with 54.0 % in the MP arm, and time to progression and OS was unaffected by advanced age, renal impairment, and adverse cytogenetics [e.g., t(4;14), t(4;16), del(p17)] . Updated results at a median follow-up of 60 months showed that the 5-year OS rate was 46 % in the VMP arm and 34.4 % in the MP arm . Of note, patients with relapse after VMP were not resistant to salvage therapies . The response rate after second-line therapy with BOR, THAL, and LEN in the VMP arm versus the MP arm was 50 %/58 %, 46 %/55 %, and 62 %/56 %, respectively . They also compared VMP patients who received BOR salvage therapy with MP patients who received BOR salvage therapy. The median survival was significantly longer in the VMP arm (56.4 months) than in the MP arm (45.4 months), suggesting that BOR-based treatment should be used as first-line therapy rather than reserving it for salvage therapy.
In terms of adverse events, PN was the major cause of discontinuation of BOR in the VISTA study. Subsequently, the Italian Study  investigated the utility of four-drug induction therapy with THAL plus VMP followed by BOR plus THAL maintenance therapy (VMPT-VT) when compared with MPB. Data from the interim analysis suggest that BOR dosing should be reduced from twice a week to once a week during the study period because of the toxicity of BOR. No difference was observed in the response rate, OS, and PFS when comparing the two BOR treatment schedules. Another study conducted by a Spanish group  compared MPB with BOR + THAL + prednisone (VTP) as induction therapy in elderly patients. BOR was administered twice a week (days 1, 4, 8, 11, 22, 25, 29, and 32) in the first cycle (6 weeks) only and was administered once a week during the next five cycles of induction therapy. After induction therapy, patients were randomized to BOR with THAL or BOR with prednisone maintenance therapy. Grade 3 or more PN occurred in 7 % in the MPB arm and in 9 % in the VTP arm during the induction phase and occurred in 2 % in the BOR with prednisone arm and in 7 % in the BOR with THAL arm during the maintenance phase.
We are currently conducting a phase II trial of MPB induction therapy, consisting of once weekly BOR induction therapy followed by a biweekly BOR maintenance regimen for elderly patients; endpoints in this study include QOL and PFS. Recent interim analysis has shown that adverse effects concerning PN rarely occurred with this BOR treatment schedule (Tokuhira M et al., personal communication).
The efficacy and safety of alternative routes of BOR administration has recently been described . A large phase III trial demonstrated that subcutaneous (SC) administration was not inferior to intravenous (IV) administration of BOR in terms of ORR after four cycles or in terms of TTP and 1-year OS. BOR-induced PN of any grade (38 vs. 53 %) and more than or equal to grade 2 (24 vs. 41 %) or grade 3 (6 vs. 16 %) occurred less frequently with SC administration than with IV administration. Therefore, SC administration of BOR may be a better injection route than IV administration.
LEN plus high-dose DEX (LD) versus LEN plus low-dose DEX (Ld) was examined in an ECOG study (n = 445) . The PR rate after four cycles of therapy was 79 % in the LD arm versus 68 % in the Ld arm. However, interim analysis at 1 year showed an overall survival rate of 96 % in the Ld arm when compared with 87 % in the LD arm. Further, 12 of 222 patients in the LD arm and one of 220 patients in the Ld arm died within the first 4 months. Therefore, the trial was terminated, and patients in the LD arm were crossed over to the Ld arm. Grade 3 or worse toxicity was reported in 53 % in the LD arm and in 35 % of the Ld arm within the first 4 months. Common toxicities were DVT (LD/Ld: 26 %/12 %), infection (LD/Ld: 16 %/9 %), and fatigue (LD/Ld: 15 %/9 %). In elderly patients, toxicity was greater with LD than with Ld.
A phase III multicenter randomized double-blind controlled trial (MM-015)  compared melphalan–prednisone–lenalidomide (MPR) induction and LEN maintenance (MPR-R) (n = 152) versus MPR induction and placebo maintenance (n = 153) or MP and placebo maintenance (n = 154). The median follow-up period was 30 months. PFS was significantly longer with MPR-R (30 months) than with MPR (14 months) or MP (13 months). The response rates associated with MPR-R and MPR were superior to that associated with MP. However, PFS associated with MPR-R was age-dependent; MPR-R significantly prolonged PFS among patients 65–75 years of age but not in those older than 75 years of age. During induction therapy, the most frequent adverse events were hematologic events; grade 4 neutropenia was reported in 35 % in the MPR-R arm, 32 % in the MPR arm, and in 8 % in the MP arm. The 3-year rate of second primary malignancies (SPMs) was 7 % in the MRR-R arm, 7 % in the MRR arm, and 3 % in the MP arm.
Several phase III trials of patients with newly diagnosed MM have reported [33–39] significantly higher ORR with MPT (approximately 30 %) when compared with MP (approximately 5 %). But the OS advantage with addition of THAL was not clear. The IFM 01-01 study (n = 232)  compared the utility of MPT versus MP in elderly patients (age ≥ 75 years). At a median follow-up of 47.5 months, median OS was significantly prolonged in the MPT arm (44.0 months) when compared with the MP arm (29.1 months) (p = 0.028). Further, median PFS was 24.1 and 18.5 months in the MPT and MP arms, respectively (p = 0.001). The HOVON group study (n = 333)  also compared MPT with MP in elderly patients with newly diagnosed MM. ORR was significantly higher with MPT (66 %) than with MP (45 %), but 55 % of the MP group and 34 % of the MPT group developed progressive disease. EFS was 13 and 9 months and OS was 41 and 31 months in the MPT and MP arms, respectively.
A meta-analysis of six randomized trials (n = 1680)  compared MPT and MP. MPT was associated with better outcomes but also with increased non-hematologic toxicities. Serious non-hematologic toxicities, older age, poor performance status, and high creatinine level were predictors of poor survival.
Optimization of maintenance therapy has been attempted in an effort to prolong the duration of response to initial treatment. Several randomized phase III studies have investigated THAL maintenance after ASCT [43–47]. There was improvement in the rate of PFS, but OS benefit was not always evident. Results from the IFM , HOVON , MRC  studies suggested that THAL has no benefit in patients with cytogenetic risk factors and may even be disadvantageous in patients with MRC del(17p). However, the TT2 study reported that THAL did indeed provide benefit in patients with cytogenetic risk groups according to the G-band method . The HOVON49 trial was the only study to demonstrate a modest benefit for thalidomide maintenance after induction therapy in ASCT-ineligible elderly patients . Because of its toxicity (e.g., PN) the average patient cannot tolerate THAL for more than 1 year. A dose of 50–100 mg/day is recommended .
LEN maintenance after ASCT was investigated in large trials conducted by the IFM (n = 614)  and CALGB (n = 460) . In the IFM trial, results at 24 months revealed an increased incidence of SPMs, and discontinuation of LEN was recommended. Significant PFS prolongation was observed in both the IFM trial and in CALGB, but 4 years after randomization, there was no difference in OS when comparing LEN maintenance and placebo. In the CALGB study, improvement in TTP and OS was clearly present at the 34-month time point. Previous use of LEN or THAL in first-line therapy has no effect on the response to LEN. The optimal dose of LEN in this setting is 10–15 mg/day, and treatment duration must not be longer than 2 years in order to minimize the risk of developing SPMs.
The efficacy of LEN maintenance after induction therapy in ASCT-ineligible patients was described in the MM-015 study . At a median observation period of 21 months, PFS was significantly longer in the MPR-R arm when compared with patients who did not receive maintenance therapy, but there was no difference in OS when comparing the two arms .
BOR as maintenance therapy is being investigated in phase III trials . A preliminary report from the HOVON-65/GMMG-HD4 trial showed that BOR maintenance was associated with an increased response rate and PFS after ASCT when compared with another arm containing THAL maintenance. But the appropriate duration or dose of BOR has not yet been determined. There are no novel agents that have been approved for use in maintenance therapy, so further study is needed.
Therapy for relapse or refractory patients
Salvage therapy should be considered for patients with relapse after ASCT, for patients with primary progressive MM, and for patients ineligible for ASCT with relapse or progressive disease after frontline therapy. Appropriate therapy for a given situation depends on the aggressiveness of the disease (e.g., presence of extensive bone disease, plasma cell leukemia, extramedullary disease, cytogenetic abnormalities) and on patient-related factors (e.g., organ function, performance status, adverse effect of prior therapy, and the availability of stem cell source) [50–52]. In these settings, the quality and duration of the response to previous therapy are thought to be the most important prognostic factors. In the case of MM relapse after a long response duration, repeat use of the previous effective therapy is generally recommended as salvage therapy [50–52]. In contrast, an aggressive disease that relapses within 6–12 months or that is refractory to frontline therapy warrants the use of an alternative regimen .
Recently, THAL, BOR and LEN have been incorporated into frontline treatment strategies. These changes raise new questions regarding the efficacy or feasibility of re-treatment with novel agents. As goals for treatment at relapse, several studies revealed that better quality of response as associated with better outcome for patients with relapsed or refractory MM, even beyond frontline therapy. For relapse more than 2 years after the first ASCT, patients should receive HDC + ASCT with the expectation of having long subsequent PFS. In the case of relapse within 1 year of ASCT, salvage treatment with novel agents (BOR, LEN, or THAL) should be conducted.
Considering the different novel drugs for treatment of MM, there are many different salvage therapy regimens. The phase III APEX trial reported that median TTP (6.22 vs. 3.49 months) and 1-year OS (80 vs. 66 %) was significantly better with BOR monotherapy than with high-dose DEX .
In an international phase III randomized study (n = 647), the combination of BOR with pegylated liposomal doxorubicin (PLD)  was compared with BOR monotherapy for relapsed/refractory MM patients. The median duration of response increased from 7.0 to 10.2 months with the addition of PLD. PLD therapy was associated with an increased incidence of grade 3/4 neutropenia, thrombocytopenia, asthenia, fatigue, diarrhea, and hand-foot syndrome when compared with BOR monotherapy.
A retrospective analysis of the efficacy of treatments at relapse was conducted in the phase III VISTA trial . That study established the superiority of VMP over MP as initial treatment for elderly patients. Response rates to subsequent bortezomib-based therapy appeared similar after VMP or MP (47 vs. 59 %). The authors concluded that patients who relapsed after treatment with a BOR-based regimen were not intrinsically more resistant to subsequent therapies when compared with those who relapsed after MP. Further, these patients can be successfully treated with subsequent BOR- or LEN- or THAL-based regimens.
The efficacy of LD compared with high-dose DEX alone in the relapsed/refractory setting was confirmed in a large phase III study (MM-009, MM-010) [55, 56]. In the MM-009 study, previously treated MM patients (n = 353) had increased OS and median TTP in the LD arm when compared with the DEX arm. Similar observations were made in the MM-010 study (n = 692), in which thrombocytopenia and neutropenia were reported as frequent adverse events. Dose reduction of LEN is needed in patients with renal dysfunction. A recent retrospective analysis of SPMs associated with LEN  reported that the incidence rate (IR, event per 100 patients) of SRMs was 3.98 in the LD arm versus 1.38 in the DEX arm. Therefore, patients with a prior history of cancer should be carefully evaluated before and during LEN treatment using standard cancer screening.
THAL has efficacy in patients with relapsed/refractory MM. THAL monotherapy was associated with an ORR of 28.2 % and a CR of 1.6 % at a dose of 200–800 mg. Thromboembolism and discontinuation due to intolerance occurred in 2.7 and 14.9 %, respectively . The use of THAL and DEX in patients with relapsed/refractory MM is associated with a higher response rate (approximately 50 % more than or equal to PR) when compared with thalidomide monotherapy . The utility of THAL monotherapy may be limited, suggesting that other cytotoxic agent should be used to improve the response rate or PFS in patients with relapsed/refractory MM. PLD and other cytotoxic regimens are promising agents for this purpose. Of note, the adverse effects of THAL were potentiated when THAL was used in combination with other agents. Indeed, DVT occurs in up to 10 % of patients treated with THAL plus DEX and in 30 % of patients treated with other cytotoxic drugs [59, 60]. Thus, patients at risk for DVT should be treated with aspirin for prophylactic purposes.
Treatment strategies for MM have changed over the last decade and now incorporate the early use of novel agents. For ASCT-eligible patients, induction therapy with novel agents and ASCT is recommended. For ASCT-ineligible patients, induction therapy with novel agents is recommended. The optimal regimen for use as maintenance therapy remains unclear. In patients with relapsed/refractory MM, novel therapy can prolong the response or survival. Adverse effects are common with novel agents for treatment of MM, and preventative measures and dose/schedule adjustment may be needed to minimize these events. The multitude of available agents means that the optimal regimen and sequence for treatment of MM remains unclear, and further clinical studies are needed to remedy this uncertainty.
Conflict of interest
The authors have no conflicts of interest to declare.