Total marrow irradiation as part of autologous stem cell transplantation for patients with multiple myeloma.

Abstract

The efficacy and safety of total marrow irradiation (TMI) plus a reduced dose of melphalan as autologous stem cell transplantation (ASCT) preconditioning for multiple myeloma (MM) patients were evaluated. The 11 patients with MM had a median age of 57 (range: 46-75) years; six of them were at standard risk and five of them were at high risk based on the Mayo Stratification of Myeloma and Risk-adapted Therapy (mSMART) standard risk factors. Before ASCT, three patients achieved stringent complete response (sCR), two patients achieved complete remission (CR), and the rest of the patients had either partial response (PR) or progressive disease. Most of the 11 patients were pretreated with melphalan 120-140 mg/m² and TMI 12 Gy. The intravenous infusion median mononuclear cell count (MNC) was 8.13 (4.16-11.84) × 10⁸/kg, and the median CD34⁺ count was 4.74 (2.51-21.98) × 10⁶/kg. The minimal residual disease (MRD) in the grafts as determined by flow cytometry (FCM) and fluorescence in situ hybridization (FISH) were negative in 10 patients but positive in the progressive patient. All patients stopped maintenance therapy after transplantation, and further observation focused on the efficacy and tolerability of the transplantation. The neutropenic and thrombocytopenia durations were 11 (7-28) and 14 (8-70) days, respectively. The primary acute non-hematological toxicities were mild oral and gastrointestinal mucositis; there were no transplant-related deaths or serious complications. Of the eight patients who did not achieve sCR before transplantation, seven converted to sCR and one converted to VGPR after transplantation. The median follow-up period was 24 (10-57.5) months. Only one patient relapsed, and the progression-free survival (PFS) was 90.9%, while the overall survival (OS) was 100%. Our preliminary results suggest that melphalan 120-140 mg/m² plus TMI 12 Gy/6f as a conditioning regimen is safe and efficient for patients with MM.