Long-Term Survival After Allogeneic Haematopoietic Cell Transplantation for Acute Myeloid Leukemia. Comparable Results From Myeloablative and Non-Myeloablative Conditioning in Young and Elderly Patients

Nonmyeloablative (NM) conditioning in allogeneic transplantation is increasingly used in patients aged over 50 years with acute myeloid leukemia (AML). In this single-center retrospective study, we report the results of NM and myeloablative (MA) conditioning in 207 consecutive AML patients. NM conditioning consisted of fludarabine 90 mg/m2 plus 2 Gy TBI, while MA conditioning was cyclophosphamide 120 mg/m2 in combination with 12 Gy TBI or 12.8 mg/kg busilvex. MA conditioning was given to 122 patients and NM to 85 patients. Median age at transplant was 39 (range 15-56) in MA patients and 59 (range 27-73) in NM patients. Donor source, cytogenetic risk, CMV antigen status recipient/donor, sex match, Karnofsky score, and body mass index were not different among MA and NM patients. Disease stages CR1, CR2, and >CR2/Primary Induction Failure (PIF) were analyzed separately. Survival of patients with advanced stage (>CR2/PIF) was short in both groups; 6.1 and 5.2 months in MA and NM, respectively. Patients in CR1 and CR2 were analyzed in details. Patient numbers in MA and NM transplants were 60 vs. 62 in CR1 and 50 vs. 17 in CR2. In CR1 and CR2 MA patients 68% and 48% received bone marrow, whereas all of the NM patients received peripheral stem cells, p<0.001. Day 100 TRM in MA vs. NM transplants was 8.3% vs. 1.6% in CR1patients and 14% vs. 5.9% in CR2 patients, which was not significantly different. Relapse incidence was comparable among the MA and NM transplants, both in CR1 and CR2 patients. The cumulative incidence of relapse at 1 year was 18.4% (CI: 5.0-28.2) versus 20.9% (CI: 5.2-31.1) in MA and NM patients transplanted in CR1, and 14.5% (CI: 5.1-24.5) versus 11.8% (CI: 0- 27.1) in CR2 patients (n.s.). The 5 year overall survival (OS) probability in the CR1 patients with MA conditioning vs NM conditioning was 63.9% (CI:51.4-76.4) vs 64.0% (CI:51.4-76.6), and among CR2 patients 51.2% (CI:36.0-66.4) vs 64.7 (CI:41.9-87.4), (n.s.).The median survival follow-up time was 55 months (range: 9-137) among CR 1 patients, and 54 months (range: 7-133) among CR2 patients. The 3-year cumulative incidence of chronic GVHD in CR1 patients was 52.8% (CI:39.9-65.8) and 41.9% (CI:29.3-54.7) in MA and NM patients, respectively. In CR2 patients, the incidences were 32.7% (CI:19.0-46.3) and 41.2% (CI:17.8-64.6). In conclusion, OS, TRM and relapse in NM transplants were comparable to MA transplants despite a truly NM regimen and a substantial age difference between groups.