Role for high-dose therapy with autologous hematopoietic stem cell support in Waldenstrom's macroglobulinemia

Despite effectiveness of standard chemotherapy regimens, complete responses are infrequent in Waldenstrom's macroglobulinemia (WM) and there are no cures. Since WM shares certain biological and clinical features with myeloma, including responsiveness to alkylating agents, evaluation of high-dose therapy (HDT) with transplant, which is effective in myeloma, is an obvious next step in an effort to achieve high response rates and improve survival. Due to the indolent nature of the disease and older patients with comorbidities, such evaluations have been infrequent in the past. We have evaluated the safety and efficacy of high-dose melphalan with peripheral blood stem cell (PBSC) support in eight patients between the ages of 45 and 69 years with WM. Adequate numbers of stem cells were collected in six patients; however, two patients with more extensive prior fludarabine therapy failed to collect adequate cells and required a second attempt at stem cell collection. Seven patients were treated with melphalan 200 mg/m(2), including two patients who received tandem transplants; one patient received melphalan 140 mg/m(2) with total body irradiation (TBI). There was no treatment-related mortality and toxicities were manageable. Recovery of bone marrow after transplant was prompt except in one patient with extensive prior use of fludarabine. All the eight patients achieved at least partial response (PR), including one complete response (CR). Five patients are alive and with out relapse (77+ to 6+ months post-transplant). Other investigators have reported similar experience suggesting safety and efficacy of HDT in WM. However, therapy with purine analogues leads to stem cell damage with decreased ability to collect adequate numbers of stem cells. This suggests that the PBSCs should preferably be procured prior to extensive use of purine analogues. Future strategies in WM will include a plan to evaluate the role of HDT along with biological agents, role of purging using rituximab, post-HDT maintenance strategies (including immunotherapy), and evaluation of nonmyeloablative regimens containing fludarabine to achieve higher response rates and improve survival.