Children's cancer group trials of interleukin-2 therapy to prevent relapse of acute myelogenous leukemia.

Purpose: Up to 80% of children with acute myelogenous leukemia treated with intensive chemotherapy achieve remission; however, a large proportion of patients develops recurrent disease. Because interleukin (IL)-2 can induce remission in patients with overt evidence of acute myelogenous leukemia, we hypothesized that it might prevent relapse when administered to patients in first remission after intensive consolidation chemotherapy. A pilot Children's Cancer Group (CCG) trial (CCG-0941) demonstrated the feasibility of this approach, and we initiated a prospective randomized trial (CCG-2961) to further evaluate the safety and potential efficacy of IL-2 therapy in preventing relapse of acute myelogenous leukemia.

Patients and methods: In trial CCG-0941, 21 pediatric patients in complete remission following induction and consolidation chemotherapy on protocol CCG-2941 received IL-2 therapy. In CCG-2961, 79 patients in complete remission were randomized as of February 1999 to receive either IL-2 (n = 39) or no further therapy. In both trials, recombinant IL-2 was given at a dose of 9 million IU/m2/d by continuous intravenous infusion for 4 days. After 4 days of rest, IL-2 was resumed at a dose of 1.6 million IU/m2/d for 10 days by continuous infusion. We monitored patients for toxicity and relapse.

Results: The majority of patients treated with IL-2 in these two trials experienced some degree of fever. Seven of 60 patients (12%) had clinically significant rashes, and grade 3 vascular leak syndrome and hypotension have each been observed in five patients (8%). Hypotension resolved promptly after treatment with intravenous fluids. No patients have experienced renal toxicity or required cardiac vasopressors or transfer to an intensive care unit; there have been no treatment-related deaths. Overall, the incidence and severity of adverse events remain similar in the two trials. Total projected accrual to the IL-2 randomization is anticipated to be 326 patients, and relapse and survival data remain blinded.

Conclusion: The dose and schedule of IL-2 used in these two trials continue to be reasonably well tolerated by children with acute myelogenous leukemia in first remission. Any conclusions with regard to efficacy must await completion of the randomized trial.