Comorbidity Score In Allogeneic Myeloablative Transplants Conditioned With Fludarabine/I.V. Busulfan (FluBu4)

The assessment of comorbidity score was previously demonstrated to predict the risk of transplant related mortality (TRM) in patients undergoing standard myeloablative allogeneic hematopoietic stem cell transplantation (HSCT). Since Flu/Bu4 regimen has been associated with limited extra-hematologic toxicity, we analyzed whether the comorbidity score may still represent a useful tool in transplant patients conditioned with this regimen. Of 52 consecutive patients who received a matched HSCT with FluBu4 at our institution, 50 were evaluable for assessing their pre-transplant comorbidity score according to the initial description (Sorror M et al. Blood 2005, 106:2912). The total dose of I.V. Bu was 12.8 mg/kg in 18 patients while in the remaining patients a targeted dose was given (AUC: 4800 μM∗min). Patients were divided in three groups: group A, score 0 (n=8); group B, score 1-2 (n=16), group C, score≥3 (n=26). The three groups did not differ significantly in age, diagnosis, previous lines of chemotherapy, type of donor and targeted vs standard dose of I.V. Bu. Patients with active acute leukemia at the time of HSCT were 12% in group A, 18% in group B and 29% in group C (p=ns). Thirteen patients (26%) died due to relapse of their malignancy and 11 (22%) due to transplant-related complications. TRM was 12% in group A, 37% in group B and 15% in group C despite the fact that the rate of acute GVHD grade II-IV was slightly higher in group C (34%), compared to groups A (12%) and B (31%). Patients in group C had a trend for higher relapse-related mortality, 38%, compared to 12% observed in each of the other groups (p=0.07). After a median follow-up of 640 days (range: 111-2065), a greater number of patients were alive and in remission in group A (75%) (p=0.04), compared to group B (50%) and C (34%). In conclusion, a higher comorbidity score correlated with worse overall survival largely due to increased relapse. However, it did not predict TRM in patients conditioned with FluBu4.