A pilot study of interleukin-2 for adult patients with acute myelogenous leukemia in first complete remission

BACKGROUND. Interleukin-2 (IL-2) has immunomodulatory effects, including stimulating the activity of cytotoxic T cells and natural killer cells, and inducing the generation of lymphokine-activated killer cells. The authors investigated whether IL-2 may improve the duration of complete remission (CR) and survival in acute myelogenous leukemia (AML) patients in first CR. METHODS. Eighteen patients were included after achieving a CR and receiving at least two courses of consolidation chemotherapy. Therapy was comprised of IL-2 4.5 x 10⁵ U/m² daily by continuous infusion (CI) for 12 weeks, plus boluses of 1 x 10⁶ U/m² on Day 8 and weekly thereafter while continuing the CI. No further chemotherapy was given after the administration of IL-2 was started. RESULTS. The median age of the patients was 50 years (range, 18-73 years), and 7 patients (39%) had an antecedent hematologic disorder (AHD). The median CR duration was 12 months, with 6 patients still alive in CR at a median follow-up of 64 months (range, 50-82 months). Long term CR by cytogenetics occurred in 2 of 5 patients with a normal karyotype (CR duration of 68+ months and 72+ months, respectively), 1 of 3 patients with t(8;21) (CR duration of 82+ months), 1 patient with inv(16) (CR duration of 67+ months), none of 2 patients with -5/-7 (1 patient died in CR after 10 months), 1 of 2 patients with abnormalities in chromosome 11 (CR duration of 60+ months), and 1 of 4 patients with miscellaneous abnormalities (CR duration of 74+ months). The median survival was 47 months. To assess the significance of these results, the authors selected two historic controls receiving long term postremission chemotherapy per each IL-2 case. The controls had remained in CR for at least as long as the cases when the latter underwent treatment initiation with IL-2 and were matched for the number of induction courses required to achieve CR, AHD, cytogenetic abnormalities, and age. Six of 18 IL-2 patients (33%) were alive in CR at 3 years compared with 7 of 36 controls (19%) (P = 0.31). Nine IL-2 patients (50%) were alive at 3 years compared with 10 controls (28%) (P = 0.13). CONCLUSIONS. These results suggest that IL-2 is tolerable in AML patients in first CR and should be studied further in future studies as a therapeutic strategy to prolong remission duration.