Randomized Study of Recombinant Interleukin-2 After Autologous Bone Marrow Transplantation for Acute Leukemia in First Complete Remission

Immunological control of acute leukemia may be achieved after allogeneic transplant. Despite promising preliminary results, the impact of immunotherapy with interleukin-2 (r-IL-2) on patients with acute leukemia (AL), in first complete remission (CR1) remains unclear. We conducted a prospective multicenter randomized trial to compare outcome in patients with AL in CR1, treated with autologous bone marrow transplantation (BMT) with or without postgraft r-IL-2. One hundred and thirty patients with AL in CR1 (myeloblastic (AML): N = 78; lymphoblastic (ALL): N = 52) were randomized at time of BMT to receive (N = 65) or not (N = 65) r-IL-2. r-IL-2 (RU 49637 from Roussel Uclaf) was started after hematological recovery, as a five cycle regimen (12 M IU/m2/day continuous infusion on day 1-5, 15-17, 29-31,43-45 and 57-59). The two groups were balanced for patient and transplant characteristics. Analysis was based on an intent to treat. Thirty-eight (59%) of the 65 patients randomized into the study group started r-IL-2 at a median of sixty-eight days (23-140) after transplant and received 77% (16-100) of the scheduled dosage. They received a median of 120 x 10(6) IU/m2 (25-156) over 10 (3-13) days during a total median period of 56 (3-78) days. With a median follow-up of 7 years (5.4-8.1 years), 79 patients relapsed (study group: 43 (66%); control group: 36 (55%): p = NS). Survival and leukemia-free survival estimates were 33% (23-45) versus 43% (22-52) and 29% (19-41) versus 36% (24-51) respectively for study and control groups (all p = NS). These results show that leukemic control after autologous BMT is not increased by r-IL-2 therapy. Further studies should investigate more appropriate r-IL-2 schedules and the possibilities offered by better antigen recognition and activated effector cells.