Abstract
Background: IgM multiple myeloma (MM) are very rare plasmaproliferative disorders representing 0.5–1.2% of all cases of MM and < 0.2% of all IgM monoclonal gammopathies. Clinical criterion are not always helpful in differentiating IgM MM from Waldenstrom macroglobulinemia. However, the presence of lytic bone lesions, absence of lymphadenopathy and/or hepatosplenomegaly, presence of translocation of the immunoglobulin heavy chain locus at 14q32 [t(11;14), t(14;16), t(4;14)], and strong expression of CD138 by the plasma cells are useful in the diagnosis of IgM MM. It has been our experience and of others that these cases have an aggressive behavior at presentation, shorter survival than IgG and IgA MM and poor response to therapy for lymphoplasmacytoid lymphomas. We present here 2 cases of IgM MM with a dramatic response to Lenalidomide and low dose dexamethasone (Rev/Dex)
Results: Baseline patient characteristics at time of diagnosis of IgM MM and therapy outcome are presented in the following 2 tables:
Table 1.
Case 1 2 Age and sex 72 (F) 73 (F) Serum M-spike (g/dL) 5.3 6.2 Urine M-spike (mg/dl/24 hrs) 72 412 Serum IgM (mg/dL) 8,590 11,000 BM plasma cells percentage 90 20 Plasma cell immunophenotyping CD138+++, partial CD20, CD56− CD138+++, partial CD20, CD56− Cytogenetics (Standard and/or FISH) Standard: normal FISH: not done on initial biopsy. On follow up there were insufficient number of plasma cells to perform test Standard: of 20 metaphases, 6 had a complex hypotetraploid karyotype with relative loss of 13q, 14, 15, 16, 20, and 22, and numerous unbalanced rearrangements. FISH: a plasma cell clone with monosomy 13 and IGH/c-MAF fusion, t(14;16). In addition, approximately 60% of plasma cells had a tetraploid clone with the same anomalies as well as relative loss of p53 Bone lesions Multiple non-traumatic spinal fractures and of stenum Several lytic lesions of long bones Renal insufficiency No No Anemia (Hbg g/dL) Yes (8.7) Yes (8.1) Hypercalcemia (Ca mg/dL) Yes (12.5) Yes (11.4) Beta 2 microglobulin (mg/dL) 5.79 8.51 Serum viscosity (cpoise) 5.9 4.8
Table 2. Best Response to therapy
Case Therapy Best Response Comments 1 Rituxan, then Fludarabine based therapy Transient response Rapid progression after partial and transient response to each therapy 1 Lenalidomide + LD-Dex sCR after cycle #6. Currently on CR 18 months later IgM declined from 8,590 to 43 mg/dL after 4 cycles of Rev/Dex. 2 Lenalidomide + LD-Dex VGPR after cycle #2 IgM declined from 11,000 to 463 mg/dL after cycle 3. Complete disappearance of M-spike in serum; BM to be done after cycle #4
Conclusions: This is the first report that we are aware of a rapid and dramatic response to lenalidomide and low dose dexamethasone in these rare cases of IgM MM with poor response to NHL-type treatment. Lenalidomide-based therapy might abrogate poor prognosis cytogenetics in this unusual subtype of MM (case #2), however, follow up for this patient is still very short.
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