Assessment of Bone Marrow Response in Waldenström's Macroglobulinemia

Waldenström macroglobulinemia: What a hematologist needs to know

“…Clinicians should be mindful of rituximab-induced paradoxical initial increase of IgM or "IgM flare" prior to response assessment [76]. Additionally, the therapy administered should be taken into account as gradual IgM decrements and selective clearance of the CD20 + B − cell compartment with sparing of the CD138+ plasma cell compartment have been observed [77,78] with agents belonging to certain classes. A substantial decrease in the IgM component may not be observed initially with monoclonal antibodies, alkylating agents, and purine analogs and persistently high IgM levels should not necessarily be interpreted as treatment failure.…”

“…A substantial decrease in the IgM component may not be observed initially with monoclonal antibodies, alkylating agents, and purine analogs and persistently high IgM levels should not necessarily be interpreted as treatment failure. The half-life of IgM is relatively brief at approximately 5 days, but the median time to maximal response may inexplicably vary from 5 to N 20 months following the completion of therapy [74,77,[79][80][81]. Conversely, mTOR, BTK, or proteasome inhibitor-based therapies may be associated with profound reductions of IgM levels without optimal bone marrow responses, underscoring the importance of repeat bone marrow biopsy and, in the context of clinical trials, preferably serial bone marrow appraisal to assess for any discordance between serum IgM and marrow response.…”

Risk stratification in Waldenström macroglobulinemia

“…However, delayed IgM monoclonal protein responses may cause important diffi culties in response assessment [61]. In addition, discrepancies between the kinetics of serum M protein reduction and the clearance of monoclonal B cells from the bone marrow have been reported [62].…”

Persistent Monotypic Plasma Cells with Absence of Neoplastic B Cell Component in a Treated Case of Waldenström Macroglobulinemia: A Sign of Residual Disease?

“…Barakat et al, also described 10 cases of WM with persistent monotypic plasma cells in bone marrow after therapy with absence of clonal B cells [5]. Varghese et al, reported the persistence of low level plasma cell clones in 5 patients with WM after chemotherapy using fludarabine alone or in combination with cyclophosphamide [6]. Goteri et al, described 2 patients with LPL who had clusters of monotypic plasma cells in BM after rituximab therapy [7].…”