Abstract
PURPOSE: Cancer and Leukemia Group B (CALGB) 9720 evaluated subcutaneous low-dose recombinant interleukin-2 (rIL-2) maintenance immunotherapy as a strategy for prolonging remission in older patients with acute myeloid leukemia (AML). PATIENTS AND METHODS: AML patients age 60 years and older in first complete remission after induction and consolidation chemotherapy were randomly assigned to no further therapy or a 90-day regimen of 14-day cycles of low-dose rIL-2, aimed at expanding natural killer (NK) cells, followed by 3-day higher doses aimed at activating cytotoxicity of expanded NK cells to lyse residual AML cells. All randomly assigned patients were included in an intention-to-treat analysis. RESULTS: A total of 163 (64%) of 254 patients who completed induction and consolidation chemotherapy on CALGB 9720 were randomly assigned to rIL-2 (n = 81) or no further therapy (n = 82); the most common reasons for lack of random assignment were patient refusal and relapse. Fifteen patients randomly assigned to rIL-2 never initiated it because of refusal, intercurrent medical problems, or relapse, and 24 patients initiated rIL-2 but stopped early because of toxicity or relapse. Grade 4 toxicities during rIL-2 therapy included thrombocytopenia (65%) and neutropenia (64%), and grade 3 toxicities included anemia (33%), infection (24%) and malaise/fatigue (14%). Forty-two patients (52%) randomly assigned to rIL-2 completed the full 90-day course. Patients in both arms had similar distributions of both disease-free (combined median = 6.1 months; P = .47) and overall survival (combined median = 14.7 months; P = .61) after random assignment. Moreover, the 42 patients who completed all planned therapy did not show prolongation of disease-free or overall survival. CONCLUSION: Low-dose rIL-2 maintenance immunotherapy is not a successful strategy in older AML patients.