Report of Consensus Panel 6 from the 12th International Workshop on Waldenström's Macroglobulinemia on Diagnosis and Management of Transformed Waldenström's Macroglobulinemia.

Histological transformation (HT) in Waldenström's macroglobulinemia (WM) is a rare complication and despite growing literature in the last years, no consensus recommendations exist. Consensus Panel 6 (CP6) of the 12th International Workshop on Waldenström's Macroglobulinemia (IWWM-12) was convened to review the current data on transformed WM and make recommendations on its diagnosis and management. The key recommendations from IWWM-12 CP6 included: (1) in case of suspected HT, tissue biopsy is the gold standard for diagnosis; (2) the initial work-up should comprise 18FDG-PET/CT for the evaluation of disease extent and, for patients with clinical suspicion or for high-risk patients (CNS-IPI, multiple and/or specific extranodal involvements), cerebrospinal fluid examination and brain MRI; (3) standard dose chemoimmunotherapy (CIT) such as R-CHOP (rituximab, cyclophosphamide, doxorubicine, vincristine and prednisone) or R-CHP + polatuzumab vedotin are the preferred front-line regimen; (4) CNS prophylaxis and consolidation with autologous stem cell transplantation (SCT) can be considered according to de novo diffuse large B-cell lymphoma (DLBCL) guidelines; (5) T-cell-engaging therapies (CAR T-cells, bispecific antibodies) should be used in the relapse/refractory setting according to international guidelines for DLBCL and local access to these therapies. Key unanswered questions include the role of TP53 abnormalities and CXCR4 mutations on the risk of HT, the prognostic role of clonal relationship between WM and HT, the optimal front-line therapy (addition of novel agents to CIT, dose-intensive CIT, consolidation with autologous SCT), and the sequence of T-cell-engaging therapies. International collaboration and consideration of and inclusion in clinical trials is critical to address these issues in a rare patient population.