6q Deletion Helps in the Discrimination Between Symptomatic Waldenström's Macroglobulinemia and Asymptomatic Forms of IgM Monoclonal Gammopathies

Abstract 4566

Cytogenetic abnormalities are present in virtually all cases of Waldenström's macroglobulinemia (WM). Among them, deletion of the long arm of chromosome 6 (6q-) is the most frequently reported in the literature, but the potential impact on disease evolution has not been completely elucidated. In this study we have analyzed the prevalence of this aberration in 203 patients with B-cell lymphoproliferative disorders (B-LPD) producing a monoclonal IgM component. Detection was evaluated by In Situ Fluorescence Hybridization in CD19+ separated cells and results were correlated with disease characteristics. The frequency of 6q21 deletion varied according to the type of B-LPD: 1/42 (2%) in IgM-MGUS, 5/69 (7%) in asymptomatic WM (aWM), 25/83 (30%) in symptomatic WM (sWM) and 0/9 in other IgM B-LPD. Within MGUS and aWM, patients with deletion of 6q displayed a high frequency of adverse prognostic features and required treatment earlier than patients with normal 6q (37 mo vs. +120 mo, p<0.05) although they finally displayed a similar overall survival. Within the sWM, those patients with del(6q) displayed parameters of high tumor burden, such as high levels of b2M and monoclonal paraprotein and more frequent anemia and hypoalbuminemia. Interestingly, there was a correlation between the presence of 6q deletion and the ISS prognostic index (frequency of 6q- among patients stratified in stages 1, 2 and 3 was 24%, 42% and 67% respectively). However, overall survival analysis did not show any difference between patients with and without 6q-, independently if the overall survival was considered globally or free of specific disease mortality. In summary, in IgM monoclonal gammopathies, 6q deletion is associated with more symptomatic forms, higher probability of treatment requirement and high tumor load, although the presence of this abnormality does not represent necessarily an adverse prognosis for OS.

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