Active immunotherapy for the treatment of acute myelogenous leukaemia: report of two controlled trials

Spontaneous remission of acute myeloid leukemia

Spontaneous remission (SR) of acute myeloid leukemia (AML) is rare. We collected all 46 reported cases of AML with SR. Fever occurred in 91.3% of cases before remission, which was largely due to pneumonia (54.5%) and bacteremia (24.2%). Pneumonia and bacteremia were significantly more common among those who achieved complete remission (CR) compared to those who achieved only a partial remission (p = 0.032). Although 88.6% of remissions were CR, the median duration of remission was only 5 months. Eight cases did not relapse during the follow-up period. The mechanism of SR in AML likely involves the stimulatory effect of systemic febrile infection on the immune system. Immediate treatment of infections and fever may contribute to the rarity of SR in AML. The results of this review improve our understanding of the important role of the immune system in countermanding AML and may provide new ideas for immunotherapy.

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.

Spontaneous remission in adult acute leukemia

A spontaneous complete remission of 34 months' duration was observed in an adult patient with acute myeloblastic leukemia. The remission occurred after a severe febrile pneumonia, which was treated with leukocyte transfusions. At relapse, chromosomal abnormalities reappeared slowly. Such spontaneous complete remissions, almost always associated with bacterial infections and blood transfusions, are extremely rare, and are usually of short duration. Previous cases are summarized, and the role of etiologic factors, including those related to the leukemic proliferation, are discussed.

Immunotherapy in the treatment of acute myelogenous leukemia (AML): rationale, results and future prospects

Patients with AML in complete remission (CR) are immunosuppressed; remission lymphocytes of at least a part of the patients are able to recognize autologous leukemic blasts; the CR represents a minimal residual disease. Thus, important conditions for a potentially successful active immunotherapy are given. Results of most earlier randomized trials on immunotherapy revealed some, but limited benefit with respect to survival. Encouraging effects, however, have been achieved by immunizing CR patients with high-dose neuraminidase-treated allogeneic blasts. Because these data have not been confirmed until now we recently initiated a randomized study utilizing identical treatment protocols. The preliminary results of the ongoing study still do not allow to draw any firm conclusions. Specific monoclonal antibodies or autologous cytotoxic T-cells may be useful tools for future immunotherapy of AML.

Adjuvant immune stimulation with Corynebacterium parvum during maintenance chemotherapy of acute myeloid leukemia. A prospective randomized study

Of 93 consecutively treated patients with acute myeloid leukemia 36 (39%) achieved complete remission (CR). Thirty-five patients were randomized to receive either maintenance chemotherapy alone (C) or a combination of active nonspecific immunotherapy with Corynebacterium parvum and chemotherapy (C + I). Maintenance therapy was given monthly for 1 year or until relapse. The median survival time was 21 months for patients treated with chemotherapy alone, compared with 30 months for patients treated with chemotherapy and immunotherapy. The median remission duration was 15 months for patients treated with chemotherapy, compared with 18 months for chemotherapy and immunotherapy group. While no statistically significant difference in remission duration or survival time could be attributed to the use of immune stimulation, a plateau of 40% long-term time survivors was defined in the chemotherapy and immunotherapy group. Age and sex were found to be the major prognostic factors for achievement of CR. No difference was found in remission duration or survival between the two different induction schedules. Neither did the morphological subtype of AML (FAB classification) or the leukocyte count at diagnosis correlate with remission rate or survival.

Immunotherapy maintenance in acute non-lymphocytic leukaemia

Between January 1975 and December 1977, 264 adult patients with acute non-lymphocytic leukaemia entered the Australian National Leukaemia Trial. Of 251 evaluable patients, three induction regimens achieved similar complete response (CR) rates. CROP (cytosine arabinoside, daunorubicin, vincristine, prednisolone) produced CR in 41% of patients, 7 and 3 (cytosine arabinoside, daunorubicin) in 42% and 7 and 3 plus hydroxyurea in 52%. Remission duration and survival were similar when induction regimens were compared. Forty-five patients reaching maintenance therapy were randomised to either chemo-immunotherapy (BCG plus intradermal leukaemic blast cells) or chemotherapy alone. The duration of CR in these two groups was almost identical, though patients receiving chemotherapy alone had prolonged survival (median 161 weeks) when compared to the chemo-immunotherapy group (84 weeks, p = 0 . 07). Institutions with less developed supportive facilities reported lower CR rates (p = 0 . 04). Leucocytosis (greater than 100 X 10(9)/1) and older age (greater than 50 years) were associated with shortened survival. The Trial has failed to show any advantage for this form of immunotherapy.

Small doses of ARA-C in the treatment of acute myeloid leukaemia: differentiation of myeloid leukaemia cells?

Three patients with acute myeloid leukaemia were treated with small doses of ARA-C (10 mg/m2/12 h, subcutaneous injections) and complete remission was obtained. The small doses of ARA-C, the progressive evolution, the absence of aplasia before remission, the simultaneous presence of normal islets of promyelocytes and leukaemic myeloblasts, favour a differentiating role for the drug rather than an antimitotic effect.

Therapy of Acute Nonlymphocytic Leukemia in Children: A Review of 73 Patients

Since 1969, 73 children with acute nonlymphocytic leukemia have been admitted for evaluation and treatment at the Institute of Hematology of the University of Rome. Various drug regimens, basically including daunomycin and/or cytosine arabinoside, were employed both for induction and maintenance treatment. Overall, the incidence of complete remission was 63 %. The availability of intensive supportive measures starting in 1974 appears to be the most likely explanation for the higher response rate observed since then. Duration of remission and overall survival were disappointingly short owing to the high frequency of bone marrow relapse. Carefully controlled clinical studies will in the future be necessary to explore better methods of preventing leukemic relapse.

Long survival in acute myelogenous leukaemia: an international collaborative study

A group of 82 adult patients with acute myelogenous leukaemia had survived in continuous first remission for more than three years was studied. These long-surviving patients were being treated at 12 referral centres in Europe and the USA, and they were compared with other patients with acute myelogenous leukaemia from 10 of these centres. There was no clear difference in the amount of induction chemotherapy or the time taken to achieve remission. Immunotherapy was not found to improve chances of long-term survival. The 82 patients were also compared with a group of 115 patients who had no appreciable difference in the number of blood or marrow myeloblasts between these two groups at presentation, but the long survivors had significantly higher initial platelet counts and were slightly younger. The long survivors also tended to have a lower total white cell count at presentation and lower granulocyte counts; there was no obvious explanation for these differences. Eight of the 82 patients relapsed from three to four years after remission and two (of 69 patients) after four to five year. Thereafter relapse was rare, and it seems likely that some of the 40 patients who have survived for five years or more are cured.