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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.
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.
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.
Herein, the Mayo Clinic Cancer Center Myeloma, Amyloidosis and Dysproteinemia and Lymphoma Disease-Oriented Groups, the multidisciplinary panels of experts with a collective experience of treating hundreds of Waldenström macroglobulinemia (WM) cases, update their evidence-based recommendations for the management of WM. Important advances have led to a broader understanding of the biology of this rare cancer since our initial risk stratification–based approach was published in 2010.1 Clinical and observational studies published or presented through December 2015 are reviewed to provide consensus recommendations for clinicians as patients with WM are infrequently encountered in practice. The guidelines are formulated using a grading system of evidence and grades of recommendations (Table 1). In the absence of adequate data or a clear superiority vis-à-vis a particular approach, we used expert consensus to formalize recommendations (eAppendix 1 in the Supplement).
Waldenström macroglobulinemia, a distinct, low-grade B-cell lymphoproliferative disorder (LPD), was initially chronicled more than 70 years ago in Jan Waldenström’s 2 landmark cases, and accounts for 1% to 2% of LPDs.2 It is predominantly a disease of elderly white men, with an overall age-adjusted incidence of 3.8/million-persons/y.3 Besides racial disparity, the epidemiologic estimates suggest genetic susceptibility and strong familial aggregation (eAppendix 1 in the Supplement). In the Surveillance, Epidemiology, and End Results data analysis (N = 4304), the median overall survival (OS) was 74 months, with a striking improvement for patients whose disease was diagnosed since 2000 (84 vs 64 months for years prior).4,5
In practice, it is important to adhere strictly to the diagnostic criteria and to exclude other LPDs before establishing the diagnosis of WM. Central to its diagnosis is the detection of IgM monoclonal protein of any size and at least 10% lymphoplasmacytic lymphoma cells in the marrow (Mayo criteria) (eTable 1 in the Supplement).1,6,7
The immunophenotypic hallmark of lymphocytes is a pan–B-cell profile, with expression of surface IgM, CD19, CD20, CD22, and CD79a antigens.7 Paired tumor/normal whole-genome sequencing was instrumental in the detection of a highly recurrent somatic mutation (leucine 265 proline) involving the myeloid differentiation primary response 88 (MYD88) gene in almost all (>90%) patients with WM.8 Another set of recently discovered nonsense and frameshift somatic mutations affecting CXCR4 are similar to those present in WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome, and are harbored by nearly one-third of patients with WM.9 Data regarding the prognostic and therapeutic implications of these mutations are beginning to unravel, and require confirmation (eAppendix 2 in the Supplement).9–12
A focused history and physical examination (eTable 2 in the Supplement) is required in all patients.
Waldenström macroglobulinemia has a heterogeneous disease course.13–16 With the median age of 69 years at presentation, and accompanying comorbidities in a substantial proportion of patients, its management can be challenging. The median disease-specific survival of 10–11 years attests to its indolent course.14,17 The International Prognostic Scoring System was developed through a collaborative analysis of treatment-naive symptomatic patients with WM (eTable 2 in the Supplement).16 Although used for patient stratification in trials, and externally validated, its value in treatment decision making remains unproven.
The overarching goals of therapy for WM are to achieve symptomatic relief and reduce further organ damage without compromising the quality of life. As WM cells of treatment-naive patients uniformly express CD20, rituximab, a generally well-tolerated chimeric anti-CD20 antibody, has become a backbone to which several other agents have been successfully integrated.20–29 Rituximab monotherapy is associated with a median progression-free survival (PFS) of 16 to 29 months, and an overall response rate (ORR) of 25% to 40% from a single 4-week cycle and 65% with an extended course of 2 4-week cycles administered 8 weeks apart.23,28 The responses may be delayed (median, 7 months).28 For patients requiring urgent therapy, rituximab is considered inferior to combination therapies. Ofatumumab, a human anti-CD20 antibody, has been successfully used in patients intolerant to rituximab.30 Literature, to date, is devoid of comparative trials involving single-agent rituximab, and our risk-adapted approach considers its use only in low-risk, symptomatic WM (Figure, A).
Therapeutic plasma exchange facilitates rapid removal of circulating IgM pentamers on an emergent basis and plays an important adjunctive—albeit a temporary—role in ameliorating hyperviscosity related symptoms until the cytoreductive therapy effectively decreases the disease burden and, in turn, its surrogate marker, the IgM protein (eAppendix 4 in the Supplement).31
The schedule and efficacy of a few commonly used regimens In WM are outlined in eTables 4 and 5 in the Supplement.
With the emergence of compelling phase 3 data from the Study Group Indolent Lymphomas (StiL) trial, bendamustine/rituximab (BR) has catapulted to a commonly used frontline regimen with manageable toxicity profile.26 A subset analysis involving patients with WM (n = 41) compared BR (n = 22 of 261) to rituximab plus cyclophosphamide, doxorubicin hydrochloride, vincristine sulfate, and prednisone (R-CHOP) (n = 19 of 253). While high ORR (approximately 95%) was evident with both regimens, better tolerability (lower rates of infections, hematologic toxic effects, PN, stomatitis, and alopecia) and, importantly, longer PFS (median 69.5 months; inter quartile range, 36.6–73.0 months) was notable with BR.26 However, a clear OS advantage with BR has not yet been demonstrated.
In a multicenter, phase 2 trial of 72 treatment-naïve patients with WM, dexamethasone-rituximab-cyclophosphamide (DRC) proved to be safe and neuropathy sparing. An ORR of 83%, with low (9%) rates of grade 3 to 4 toxic effects, was noted (eTable 5 in the Supplement).32 Importantly, therapy-related myelodysplastic syndrome has not been documented so far, and the majority of those requiring retreatment demonstrated a meaningful response (ORR, 82%) to rituximab-based salvage therapy.33 Given the modest toxicity profile and stem cell–sparing effect, DRC was considered the initial regimen of choice in our guidelines previously.1
The caveats with the aforementioned regimens are that DRC was evaluated in a single-arm study and the StiL study did not compare eBR with the most effective contemporaneous regimens for WM.26,32 Further more, despite the high ORR, the suitability of R-CHOP as a frontline regimen is questioned, given the concerns of vinca alkaloid–associated neurotoxicity, potential for cardiotoxicity, and inferiority of the CHOP backbone to even older agents such as fludarabine phosphate.
A large phase 3 trial (WM1) has demonstrated superiority—Including OS advantage—of oral fludarabine to chlorambucil in treatment-naive patients with advanced WM.34 In contrast to the reports from prior retrospective studies, second cancers were more frequent with chlorambucil therapy (6-year cumulative incidence rate 20.6% vs 3.7% with fludarabine).34 Notwithstanding the unavailability of oral fludarabine in the United States, and the limited practical applicability of the WM1 trial comparing monotherapies in the era of rituximab-based combinations, this study illustrates that the choice of initial therapy significantly affects OS.
Three small phase 2 studies have evaluated bortezomib-based combinations in the frontline setting, showing an ORR of 81% to 96%.22,24,35 Although bortezomib, the first-in-class proteasome inhibitor, elicits rapid (median, 1.4–3 months) and durable responses, an underlying PN at diagnosis, as well as an increased predisposition for PN even with its absence at baseline, raises concern for the use of this neurotoxic agent in patients with WM. In the WMCTG05-180 trial, a majority developed PN (overall, 69%; grade 3, 30%), resulting in premature discontinuation in 61% of patients.35 To mitigate the risk of PN the bortezomib-dexamethasone-rituximab regimen was modified, transitioning patients from twice to once weekly intravenous administration of bortezomib beyond the first cycle.22 Reduced frequency of administration decreased neurotoxic effects (grade 3, 0%–7%) and resultant discontinuation (approximately 8%) but compromised the response (major response rate, 65%–68%).22,24 The ongoing R2W trial (NCT01592981), using a potentially less neurotoxic, subcutaneous route for bortezomib, compares bortezomib-containing and fludarabine-cyclophosphamide-rituximab regimens, and could help clarify any potential advantages of using rituximab-bortezomib combination over conventional chemoimmunotherapy. Newer proteasome inhibitors (eAppendix 4 in the Supplement) have the potential to overcome some of the bortezomib-associated challenges.
Trials assessing the irreversible Bruton tyrosine kinase inhibitor, ibrutinib, in the frontline setting are currently under way (NCT02165397).
A single retrospective study supports the use of rituximab maintenance In WM, but the results of the StiL NHL7-2008 trial addressing this important issue are awaited (eAppendix 4 in the Supplement).
Waldenström macroglobulinemia remains an incurable disease with an inexorable propensity for relapse. A small proportion of patients have primary refractory disease. Management decisions for the patients with relapsed disease hinge on a multitude of factors, including the magnitude and durability of remission with prior therapy, patients’ candidacy for autologous stem cell transplantation (ASCT), the type and number of prior regimens and their tolerability, the patients’ preferences, the pace of relapse, the impact on future treatment options, and most importantly, the need to reinitiate therapy. The study involving DRC demonstrated substantially longer time to next therapy (TTNT; median, 51 months) than PFS (median, 36 months), underscoring that biochemical progression does not equate with the requirement to reintroduce therapy.33 The indications for initiating treatment in relapsing patients are largely similar to those for the treatment-naive patients.
Similar to the frontline setting, comparative trials to determine the optimal approach are nonexistent. Retreatment with the initial therapy can be considered if the TTNT is at least 3 years from the commencement of previous therapy (Figure, B). Bendamustine, as monotherapy and in combination with rituximab and/or ofatumumab, has shown an ORR of 83%in relapsed-refractory WM but leads to prolonged myelosuppression in patients previously exposed to a nucleoside analog.36,37 More recently, an Italian retrospective study of patients with relapsed-refractory WM (n = 71) reported an ORR of 80% with BR, with the median PFS not being reached after a median follow-up of 19 months. Transformation or therapy-related myelodysplastic syndrome/acute myeloid leukemia was not observed.37
The appropriate subset of patients with WM who should be offered ASCT, as well as its optimal timing, is unestablished, with indolent disease course, advanced age, and multiple comorbidities at presentation rendering a large proportion of candidates transplant ineligible. Moreover, its rarity hampers conduction of trials comparing ASCT with alternative approaches.
Despite the lack of data to support survival advantage with myeloablative therapy in WM, several studies have reported encouraging results suggesting long-term disease control with ASCT.38,39 In the European Bone Marrow Transplant Registry series (n = 158), the disease chemosensitivity at ASCT affected outcome. The modest nonrelapse mortality rate (3.8%), with estimated 5-year PFS and OS rates of 40% and 69%, respectively, attest to the tolerability and efficacy of ASCT.39
In patients who are potentially ASCT eligible, particularly those presenting with active disease at age 70 years or younger, consideration should be given to stem cell harvest in first remission after a low tumor burden has been achieved. Without evidence supporting survival benefit, ASCT is best avoided as a primary consolidative approach outside a trial. Our preferred strategy is to use cryopreserved cells early in the relapsed setting in chemosensitive disease because the efficacy of ASCT is markedly reduced in heavily pretreated (≥3 lines of prior therapy)/refractory WM. Despite graft-vs-lymphoma effect and high complete response rates (62%–66%), the associated toxic effects and the prohibitively high 1-year treatment related mortality rates of upto 44%limit the use of allogeneic transplantation (eAppendix 4 in the Supplement).38
A phase 1 trial of advanced B-cell malignant neoplasms demonstrated strong activity of ibrutinib in the WM cohort,40 prompting a phase 2 study with relapsed-refractory disease (n = 63).41,42 The convincing results of this trial led to ibrutinib’s approval for WM in the United States and the European Union in 2015. Rapid reduction in IgM (median time to response, 1.2 months), in parallel to the hematocrit increase, was evident. While MYD88 L265P–Bruton tyrosine kinase complex promotes cell proliferation and makes cells susceptible to ibrutinib therapy, the presence of CXCR4 WHIM confers resistance. Significant activity (ORR, 95.5%) was noted, with highest response rates witnessed in those harboring MYD88 L265P and CXCR4 wild-type (WT) genotype.41,42 Although superior PFS and improved tolerability was noted in the less pretreated patients (as expected), data with ibrutinib for treatment-naive WM are currently unavailable. Importantly, complete responses have not been observed and the follow-up remains short. The estimated 2-year PFS and OS of 69% and 95%, respectively, are comparable to those of other salvage therapies. Notably, IgM-mediated PN improved or stabilized with ibrutinib treatment, and IgM flare was not observed. Clinicians should be mindful of the drug-drug interactions and toxic effects associated with ibrutinib treatment, including neutropenia, thrombocytopenia, postprocedural hemorrhage, epistaxis with concurrent fish oil use, and a trial fibrillation in patients with a history of arrhythmias. Despite these limitations, there is potential to further expand the use of this oral, stem cell–sparing agent as the results of ongoing trials of ibrutinib-based combinations unfold (NCT02165397).43
The purine analogs cladribine and fludarabine phosphate are effective against relapsed-refractory WM as single agents (ORR, 31%–55%)44–46 as well as combination therapies25,27,47 (ORR, 79%–96%; complete response, 12% with fludarabine-cyclophosphamide-rituximab and 25% with cladribine-rituximab). However, toxic effects, including stem cell toxicity, prolonged myelosuppression/immunosuppression with infections, and secondary malignant neoplasms/transformation have limited their use.48
The PI3K/AKT/mTOR pathway is another constitutively activated pathway regulating cell metabolism, proliferation, survival, and angiogenesis in WM.49 Everolimus, an oral mTORC1 inhibitor,50 can produce responses bearing a striking resemblance to those from ibrutinib treatment, with rapid IgM reduction (median time to response, 2 months; median duration of response, not reached) in the face of persistent marrow infiltration. However, everolimus causes mucositis, diarrhea, fatigue, and dose-dependent myelosuppression.
Substantial recent progress, particularly the seminal discoveries of MYD88 and CXCR4 mutations, has paved the way for an exciting era in WM treatment. Extensive evaluations are ongoing to determine the precise role of these mutations. Furthermore, the therapeutic armamentarium against WM is poised to expand as the efficacy of several new, potentially effective agents, including the second-generation BCR inhibitors, oral proteasome inhibitors (ixazomib and oprozomib), B-cell lymphoma 2 inhibitor (venetoclax), glycoengineered anti-CD20 antibody (obinutuzumab), and programmed cell death 1 inhibitors, is being examined. In particular, targeted therapies need to be developed for the MYD88 WT patient population.
We periodically update our evidence-and consensus-driven recommendations at http://www.mSMART.org to present a coherent management approach as new clinically relevant data emerge.
Conflict of Interest Disclosures: Dr Kapoor has received research funding from Takeda (Institution), Onyx (Institution), and Celgene (Institution), and consulting fees from Celgene and Sanofi (Institution). Dr Ansell has received research funding from Bristol-Myers Squibb, Celldex, Merck, Affimed, and Seattle Genetics. Dr Fonseca has received consulting fees from Celgene, Genzyme, Bristol-Myers Squibb, Bayer, Lilly, Onyx, Binding Site, Novartis, Sanofi, Millennium, and Amgen; has research funding from Onyx; and is a member of the scientific advisory board of Applied Biosciences. Dr Kumar has received honoraria from Skyline Diagnostics. Research support from Abbvie, Celgene, Novartis, Amgen, Takeda, Sanofi, and Janssen has been provided to Institution for conduct of clinical trials on which Dr Kumar serves as a principal investigator. Dr Mikhael has received research support from Celgene, Onyx, Abbvie, and Sanofi. Dr Witzig reports receiving research funding from Celgene (Institution), Novartis (Institution), Spectrum Pharmaceuticals (Institution), and Acerta Pharma (Institution). Dr Mauermann has received research support from Alnylam and Ionis pharmaceuticals, and honoraria from Ionis. Dr Dispenzieri has received research support from Celgene, Millenium, Pfizer, Jannsen, and Alnylam. Dr Ailawadhi has served as a consultant for Novartis Pharmaceuticals, Amgen Pharmaceuticals, Pharmacyclics, Inc, and Takeda, and has received research funding from Pharmacyclics, Inc. Dr Stewart has received research support from Celgene and Takeda and consulting fees from Novartis and Takeda. Dr Lacy receives research funding from Celgene. Dr Dingli has received research funding from Takeda, Karyopharm, and Amgen. Dr Grogan has received research support from Pfizer and consulting fees from Prothena. Dr Bergsagel has received research support from Novartis and Constellation Pharmaceuticals and consultant fees from Amgen, Janssen, Sanofi- Aventis, Mundipharma, and Bristol-Myers Squibb. Dr Lin receives research funding from Janssen. Dr Gertz has received research support from Ionis Pharmaceuticals and Prothena and honoraria from Celgene, Millennium Pharmaceuticals, and Novartis. Dr Reeder has received research support from Celgene, Novartis, and Millennium. No other disclosures are reported.