Pocket Oncology (Pocket Notebook Series), 1st Ed.

WALDENSTRÖM MACROGLOBULINEMIA (WM)

Patrick W. Burke and M. Lia Palomba

Definition

B-cell malignancy w/BM infiltration by lymphoplasmacytic cells plus an IgM monoclonal gammopathy. May have extramedullary involvement (LNs, liver, spleen, kidney, etc.).

Considered a LPL per 2008 WHO Classification of Lymphoid Neoplasms.

Epidemiology

Overall Incidence: ∼3 per million persons per y.

1500 new cases diagnosed each y in the United States.

Strong familial predisposition: Most cases sporadic. Some reports ∼20%

WM pts have ≥1 first-degree relative w/B-cell neoplasm (Ann Oncol 2006;17:488; Clin Cancer Res 2007;13:5063; Blood 2008;112:3052).

HCV: Implicated in some studies, esp w/type II (mixed) cryoglobulinemia.

IgM MGUS: Confers 46-fold ↑ RR to develop WM (Blood 2010;115:4464).

Biology (Curr Opin Hematol 2011;18:260)

• B-cell arrested in germinal center, after somatic hypermutation, before terminal differentiation to PC.

VH gene somatic Mt. No isotype class switch.

• Del 6q: Most common cytogenetic abnormality (∼55%).

A/w worse prognostic signs: ↑ B2 MG, ↑ M-spike, anemia, & hypoalbuminemia.

BLIMP-1 (6q21) regulates PC differentiation.

• WM also a/w trisomy 4, trisomy 5, monosomy 8, & Del 20q.

• Evolving discovery MYD88 gene involvement on 3p22 locus.

MYD88 adaptor protein → mediates TLR-4 & IL-1 receptor signaling.

∼ 90–95% MYD88 exon 5 L265P Mt in WM (N Engl J Med 2012;367:826).

>90% MYD88 locus (3p22) involved in WM: L265P or 3p22 gain (Blood 2013).

→↑ IRAK-mediated NF-kB signaling & ↑ JAK/STAT3 signaling.

NF-kB chronic stimulation possibly earliest oncogenic event.

• Activation of PI3K/Akt/mTorr pathway w/o specific activating Mt.

• Likely strong role of external stimulation via BM microenvironment.

↑ Cytokine & chemokine upregulation in WM (BLyS, IL-6, CD40 ligand, BAFF, APRIL, & SDF-1).

• ↑ BM angiogenesis factors

• NF-KB inhibition by proteasome inhibitors has preclinical & clinical efficacy.

Disease Manifestations

• Related to WM neoplastic cell infiltration and/or physiochemical or immunologic properties of IgM.

• WM neoplastic cell burden mostly in BM. <15% p/w significant LAD or organomegaly. BM infiltration → cytopenias.

IgM physiochemical/immunologic properties (Blood 2009;114:2375).

Hyperviscosity: IgM pentameric structure → HAs, CN palsies/neurodeficits, blurred vision, retinal hemorrhages, epistaxis, ICH, AMS, LE cramping.

Peripheral neuropathy: IgM autoAb to (1) MAG, (2) GM1, or (3) nerve sheath sulfatide moieties → sensorimotor neuropathy, painful neuropathy, ataxic gait, foot drop.

Type I Cryoglobulinemia (up to 20%; 5% sx): IgM precipitation w/cooling → Raynaud phenomenon, acrocyanosis, digital ulcers, purpura, & cold urticaria.

Type II Cryoglobulinemia: IgM against IgG Fc → purpura, arthralgias, renal failure, & sensorimotor neuropathies.

Cold Agglutinins (∼10%): IgM against RBC Ag → AIHA, Raynaud phenomenon, acrocyanosis, & livedo reticularis.

Multiorgan Dysfunction: IgM amorphous aggregation & tissue deposition → Derm (bulli, papules, Schnitzler syndrome); GI (diarrhea, ↓ absorption, GIB); Renal (proteinuria, light chain deposition disease, renal failure).

Multiorgan Dysfunction: Amyloid deposition → fatigue, ↓ wt, edema, organomegaly, macroglossia, peripheral/autonomic neuropathy, CHF, cardiac dysrhythmias, proteinuria, renal failure, & liver dysfunction.

Other ROS (Blood 2009;114:2375).

Recurrent sinopulmonary infxn (↓ IgG & IgA).

Thrombosis (APLA syndrome).

Bruising/bleeding diathesis (↓ plats, acquired vWD).

Workup

• Essential: Hx & physical, CBC w/diff, metabolic panel + LFTs, quantitative Igs (IgM level under warm bath if cryoglobulin +), SPEP, SIF, SFLC, B2 MG, serum viscosity, Hepatitis B & C testing, unilateral BM aspirate & bx (aspirate heme-path review, flow cytometry, & cytogenetics), & CT C/A/P.

• Nonessential: Warranted/useful in certain circumstances → cryoglobulins, cold agglutinins, APLA syndrome Abs, Anti-MAG & Anti-GM1 abs, electromyelogram, neurology consult, retinal exam (if ↑ viscosity s/s), fat pad bx w/congo red stain or BM bx for amyloid, & MRI brain ± anti-Hu/anti-hsp 70 Abs (hearing loss).

Pathology

• Defined as IgM LPL. Clonally related lymphoplasmacytic cell population, located mostly in BM.

Small lymphocytes w/evidence of plasmacytoid/PC differentiation.

Secretes IgM M-protein. Most LPL are WM (IgM). <5% are IgA or IgG.

• Immunophenotype (IHC & flow cytometry): CD19+, CD20+, CD 22+, CD79+, sIgM+.

20% WM: CD5+, CD10+, or CD23+ (Clin Lymphoma 2005;5:246).

Staging

• Little use for Ann Arbor staging since BM involvement by definition.

• ISSWM informs median survival & possibly trajectory of disease.

 Not an independent determinant for tx (Blood 2009;113:4163).

Treatment

• WM is an indolent lymphoma→ tx indicated only if sxs present: Cytopenias, hyperviscosity, neuropathy, organomegaly, bulky LAD, cold agglutinin disease, cryoglobulinemia, amyloidosis.

• Not curable w/conventional therapies (CT or HDT → ASCR).

• Like other indolent lymphomas, possibly curable w/allogeneic HSCT. But not recommended outside clinical trial in WM for ↑ risk disease.

• ↑ Viscosity sxs, serum viscosity > 3.5 cP, or IgM > 5 g/dL → urgent plasmapheresis before CT (2–3 courses → ↓ IgM 30–60%).

• CT regimen choice first depends on if candidate for ASCR.

If ASCR candidate → avoid nucleoside analogs (difficulty w/stem cell collection & ↑ risk of MDS/AML/disease transformation) & oral alkylators.

• Anti-CD20 mAb (rituximab/ofatumumab) cornerstone most regimens. But → ↑ IgM transiently (IgM flare∼40–50%) → may ↑ sxs.

• Bortezomib → ↓ IgM incommensurate to actual ↓ neoplastic cell burden due to ↓ protein synthesis. Highly effective in combination regimen. Be wary of worsening neuropathy.

• R-CP, R-CVP, & R-CHOP → similar efficacy but ↓ tox w/R-CP (Clin Lymphoma Myeloma 2009;9:62). Bendamustine ↑ efficacy.

• HDT → ASCR: 45–65% DFS at 5 y. Not curative. Often used in chemosensitive, relapsed disease.

• Remarkable activity pathway inhibitors: Everolimus (mTorr inhibitor). Ibrutinib (BTK inhibitor).