Interleukin-2 therapy in relapsed acute myelogenous leukemia

Several studies have been conducted in Italy to assess the activity of recombinant interleukin-2 (rIL-2) in patients with relapsed-refractory acute myelogenous leukemia (AML) and in AML patients in second complete remission (CR) who are not eligible for standard therapy. We report here the updated results of those studies.

Since 1988, a total of 24 patients with relapsed-refractory AML and < or = 30% bone marrow blasts (median blastosis, 15%), who were not suitable for further chemotherapy, were treated with a daily dose-escalating protocol of rIL-2 (8-18 x 10(6) IU/m2 x 5 days) by continuous intravenous infusion with a 72-hour rest period between each cycle. Patients achieving a response to induction therapy received subcutaneous maintenance rIL-2 therapy at lower doses for 5 days/month. Based on these encouraging results, a prospective randomized trial was initiated by the Italian cooperative groups GIMEMA (Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto) and AIEOP (Associazione Italiana Ematologie e Oncologia Pedietrica) to assess the efficacy of this rIL-2 regimen in AML patients in second CR. Of 264 AML patients enrolled, 146 patients (55%) achieved a second CR in response to mitoxantrone, etoposide, and cytarabine; 32 patients who were not eligible for transplantation were randomized to rIL-2 (15 patients) or no treatment (17 control patients). Accural goals were never reached, however, due to low recruitment.

In the pilot study, 13 patients (54%) obtained a CR, which persists in eight patients with a median follow-up of 64 months (range, 1-110 months) on maintenance rIL-2. In the randomized study, a trend in favor of improved disease-free survival was observed in the rIL-2 arm.

Encouraging results have been obtained with rIL-2 therapy in AML patients with relapsed-refractory disease and limited blastosis and in patients in second CR. These results have prompted a large, multicenter, randomized study to evaluate the efficacy of high-dose rIL-2 therapy in AML patients with advanced disease but limited blastosis in relapse following cytoreductive chemotherapy or autologous transplantation.