Allogeneic Hematopoietic Stem Cell Transplantation (HSCT) in the Treatment of Acute Lymphocytic Leukemia (ALL) in 126 Adults: Impact of Donor Source on Leukemia Free Survival (LFS).

White blood cell (WBC) count and specific cytogenetic abnormalities at diagnosis, patient age and disease status at HSCT have previously been identified as risk factors associated with LFS in patients with ALL. As the use of umbilical cord blood (UCB) is relatively new, particularly for adults, we sought to evaluate the relative impact of donor source. In this single center study, 126 adults aged 18–61 (median 31) years (yrs) underwent myeloablative conditioning (cyclophosphamide 120 mg/kg and total body irradiation 1320–1375 cGy based regimen in 92%) followed by allogeneic HSCT. Stem cell source was an HLA matched related donor (MRD) in 85, HLA matched unrelated donor (URD:M) in 15, HLA mismatched unrelated donor (URD:MM) in 14 and HLA 0–2 (A, B, DRB1) mismatched UCB in 12. At the time of HSCT, 64 patients were in CR1, 51 in CR2, and 11 patients in ≥ CR3; 20 pts had T-lineage disease; 38 pts (30%) had either t(9;22)(n=28), t(4;11) or t(1,19) (n=10) with the remainder (70%) having normal cytogenetics. WBC ≥ 30 x 10⁹/l at diagnosis was documented in 50%. Demographics, disease characteristics at initial diagnosis and transplant variables were similar in all 4 groups except: year of transplant after 1996 and use of growth factor for all UCB recipients.

As a consequence of low TRM, OS and LFS were superior after UCB transplants. In multiple regression analysis, 5 independent risk factors were significantly associated with poorer OS: use of URD:M (RR 3.8, 95% CI 1.1–13.8, p= 0.04) and URD:MM (RR 4.9, 95% CI, 1.3–19.1, p= 0.02), ≥ CR3 at HSCT (RR 3.0, 95% CI, 1.1–8.8, p= 0.04), WBC >30 x 10⁹/l (RR 2.4, 95% CI, 1.4–4.1, p<0.01), cytomegalovirus (CMV) seropositive recipient and donor (RR 4.0, 95% CI, 2.0–7.9, p<0.01), and ≥ 2 induction regimens to achieve initial CR (RR 2.7, 95% CI, 1.2–5.9, p= 0.01). Patients who developed grade II–IV acute graft versus host disease (GVHD) had significantly lower mortality rates (RR 0.4, 95% CI, 0.2–0.7, p<0.01). There was no impact on OS by year of transplant or use of growth factor. Variables associated with poor LFS were identical to those for OS, and GVHD was again associated with improved LFS. These results support the use of UCB as an alternative stem cell source for adults with ALL with results comparable to outcomes observed with MRDs. In addition, GVHD is associated with improved LFS suggesting a significant graft versus leukemia effect with all donor graft sources.