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 ϫ 10 5 U/m 2 daily by continuous infusion (CI) for 12 weeks, plus boluses of 1 ϫ 10 6 U/m 2 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 68ϩ months and 72ϩ months, respectively), 1 of 3 patients with t(8;21) (CR duration of 82ϩ months), 1 patient with inv(16) (CR duration of 67ϩ months), none of 2 patients with Ϫ5/Ϫ7 (1 patient died in CR after 10 months), 1 of 2 patients with abnormalities in chromosome 11 (CR duration of 60ϩ months), and 1 of 4 patients with miscellaneous abnormalities (CR duration of 74ϩ 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 ϭ 0.31). Nine IL-2 patients (50%) were alive at 3 years compared with 10 controls (28%) (P ϭ 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.