Immunotherapy in acute myelogeneous leukemia (AML)--a tool for maintaining remission?

Twelve trials of adjuvant immunotherapy in patients suffering from AML have been analyzed and compared to results from experimental studies. The analysis presents evidence suggesting that the immune response to leukemia cells exists in a state of balance; this appears to be regulated by the dose of antigen and the state of the cells used to immunize the patients. The injection of high doses of live allogeneic leukemia cells produced a significantly prolonged duration of the first remission in in AML patients. Immunization with high doses of irradiated and dead cells induced some prolongation of the remission phase and survival time, although the percentage of survivors after 3 years was not increased in these groups as compared to non-immunized patients. Immunization by the same route using a 100-fold lower amount of leukemia cells afforded no protection against relapse of the disease during the maintenance phase. A few patients even developed the relapse earlier than did patients treated with chemotherapy alone. Our understanding of the immune responses to malignant cells has increased considerably during the past 2 decades due to various observations. The results obtained with active immunotherapy of the AML patients during the same period agree well with experience from laboratory studies. Thus the results confirm the potential of an immunological interaction between the leukemia cells and the patient. Consequently, it seems likely that the addition of immunotherapy to the treatment of patients with AML might be effective and the tool for maintaining the phase of remission by up-to-date immunological engineering.