How long can we give interleukin-2? Clinical and immunological evaluation of AML patients after 10 or more years of IL2 administration

We have treated 20 patients, affected by acute myelogenous leukemia in advanced phase of the disease, with intravenous high-dose recombinant interleukin-2 (IL2) as induction treatment, achieving a complete remission (CR) in 11/20 of patients (55%). All CR patients were planned to receive a maintenance program with lower subcutaneous doses of IL2 until relapse. Currently, 5/11 patients are alive in continuous complete remission with a minimum follow-up of 9 years from IL2 induction. In the aim to investigate the treatment's side-effects during or after prolonged IL2 therapy, we decided to submit these patients to a clinical and immunological evaluation. Four patients have been evaluated as one, who independently stopped IL2 after 6 years, refused the check-up. No organ-specific treatment sequelae that may decrease the quality of life or may be life-threatening were found, concerning renal, liver and cardiovascular function. Endocrine abnormalities were detected in three patients, the most serious being a severe hypothyroidism, which prompted cessation of IL2 maintenance after 6 years and required thyroid supplementation treatment. Immunological studies were carried out prior to the last IL2 cycle and showed high levels of CD3-positive T cells expressing the IL2 receptor alpha chain (CD25), both in the peripheral blood and in the bone marrow. Our study shows that low-dose IL2 can be given for a prolonged period of time without serious organ-specific late sequelae and with a good quality of life.