A Low Intensity Protocol of Fludarabine, Busulfan and Cyclophosphamide Reduces Toxicity without Compromising Engraftment in Children Undergoing Allogeneic Bone Marrow Transplantation for Beta Thalassaemia Major.

Busulfan (Bu) and Cyclophosphamide (Cy) based conditioning protocols are associated with significant morbidity and mortality in Class III (Pesaro classification) patients with beta thalassaemia major undergoing allogeneic stem cell transplantation. After IRB clearance and informed consent, we have developed a new low intensity protocol using fludarabine 30mg/m²/day for 5 days (Day - 15 to Day -11), busulfan 14 mg/kg over 4 days (Day -10 to -7) and cyclophosphamide 160 mg/kg over 4 days (Days -5 to -2). Graft versus host disease (GVHD) prophylaxis consisted of cyclosporine (5mg/kg/day) in 2 divided doses starting Day -4 and methotrexate 10 mg/m² on Day +1 followed by 7 mg/m² on Day +3, +6 and +11. Between January and July 2006, 14 children with Class II (n = 5) or Class III (n = 9) beta thalassaemia major were treated with this protocol. The median age was 10 years (range: 3 – 13). All patients had HLA matched related donors [sibling (13) or family (1)] with a median age of 4 years (range: 2 – 35). Ten (71%) of these transplants were sex mismatched. One patient expired on Day +10 due to an intracranial bleed while 13 (92.8%) engrafted. The median time to ANC > 500/mm³ was 17 days (range: 14–20) and platelet count > 20,000/mm³ was 25 days (range: 11 – 49). One patient had graft rejection. Two patients (14%) had grade 2 hemorrhagic cystitis and veno-occlusive disease each that resolved with conservative management. None of the patients had grade IV mucositis while 1 patient has a grade II gastro-intestinal bleed lasting 2 days that resolved with transfusion support. Acute GVHD (grade I – II) was seen in 5 patients (41.6%) and resolved in all with corticosteroids. Febrile neutropenia occurred in all but only 2 patients had a documented infection. The day 30 chimerism was complete in 10 patients (77%), > 90% donor chimerism in 2 (15.3%) with rejection in 1 patient (7.7%). At a median follow up of 4 months (range: 1–6), the overall survival (OS) is 92.8% and the disease free survival is 85.7%. We compared engraftment and toxicity with 167 patients with Class II and III Thalasssaemia treated with Bu16/Cy200 (n=116) or Bu600 mg/m²/ Cy200 (n=51) and found that the engraftment was not delayed but there was significant reduction in VOD (14% vs 53%; p=0.005) and gastrointestinal bleeding (7% vs 39%; p=0.021) with this new protocol.

Conclusion: A low intensity protocol incorporating reduced doses of busulfan and cyclophosphamide in combination with fludarabine is associated with reduced toxicity and improved survival in children undergoing allogeneic BMT for Thalassaemia. Long term follow up is required to assess late toxicity and graft function.