Total Marrow Lymphoid Irradiation/Fludarabine/ Melphalan Conditioning for Allogeneic Hematopoietic Cell Transplantation

Reduced-intensity conditioning (RIC) regimens for hematopoietic stem cell transplantation (HCT) can reduce morbidity and mortality, but patients with advanced disease may require alternative approaches. In an initial report of RIC with fludarabine (FLU) and melphalan (MEL) with total marrow lymphoid irradiation (TMLI) in HCT for advanced hematologic malignancies in 33 patients, we found that the addition of TMLI to RIC was feasible and safe. Here we report long-term outcomes for these patients. This prospective study included 61 patients treated with TMLI to a dose of 12 Gy (1.5 Gy twice daily for 4 days), FLU (25 mg/m2/day for 5 days), and MEL (140 mg/m2/day for 1 day). Overall survival (OS), event-free survival (EFS), cumulative incidence of relapse (CIR), and nonrelapse mortality (NRM) were measured from the date of HCT. Survival outcomes were analyzed using Kaplan-Meier analysis. Patients were categorized as low/intermediate or high/very high risk using the Disease Risk Index. The median follow-up was 7.4 years. The majority of patients had acute leukemia (72%); 49% had high/very high-risk disease. The median patient age was 55 years (range, 9-70 years). Two-year OS, EFS, CIR, and NRM were 54% (95% confidence interval [CI], 41%-66%), 49% (95% CI, 36%-61%), 21% (95% CI, 13%-35%), and 30% (95% CI, 20%-43%), respectively. Five-year OS, EFS, CIR, and NRM were 42% (95% CI, 30%-54%), 41% (95% CI, 28%-53%), 26 (95% CI, 17%-40%), and 33% (95% CI, 23%-47%, respectively). Acute (any grade) and chronic (limited or extensive) graft-versus-host disease occurred in 69% and 74% of patients, respectively. The most common toxicity was mucositis. The addition of TMLI to FLU/MEL conditioning was well tolerated, with favorable outcomes. Dosage escalation of TMLI or other modifications may be needed to improve disease control.