Post-Treatment Bone Marrow Residual Disease > 5% by Flow Cytometry Is Highly Predictive of Short Progression-Free and Overall Survival in Patients With Waldenström's Macroglobulinemia

To assess the value of bone marrow (BM) assessment by flow cytometry FCM after therapy in the clinical outcome of WM patients, we analyzed 42 WM patients who were evaluated before and after therapy. Patients were studied with a panel that always included the CD19, CD22, CD25, and κ/λ light chain immunoglobulin monoclonal antibodies. The mean of abnormal B-cells in the pre-therapeutic BM was 17.8% ± 12.1%, which decreased was after therapy to 5.4% ± 0.7% (P = .049). A linear correlation was seen between the better quality of response and the reduction in the tumor B-lymphocyte counts at the BM, since the ratio of abnormal B cells between pre and posttherapy BM was 1172.17, 221.64, 3.37, 1.03, and 0.56 for responses complete, partial, minor, stable disease and progression, respectively (P < .001). Intensive and rituximab-containing therapies correlated with deeper tumor cell reductions. Finally, the B-cell decrease correlated with the better overall and progression-free survival.