Transformation and progression of Waldenström's macroglobulinemia following cladribine therapy in two cases: natural evolution or iatrogenic causation?

We report two cases of Waldenström's macroglobulinemia with an unusual aggressive transformation following treatment with cladribine (2-chlorodeoxyadenosine, 2-CdA), a purine analogue. The first patient developed transformation to a diffuse large-cell non-Hodgkin lymphoma, while the second developed extensive extramedullary involvement. Both patients displayed rapid progression following transformation and were refractory to chemotherapy. Both patients were pretreated with multiple courses of prednisone and chlorambucil, and transformation occurred shortly after therapy with cladribine. We propose that immune suppression from alkylating agents and purine analogues may have contributed to the unusual progression, resulting in a dismal outcome. 2006 Wiley-Liss, Inc.