Evolving modalities of treatment with interferon alfa-2b for Ph1-positive chronic myelogenous leukaemia

Practical guidelines for the management of chronic myelogenous leukemia with interferon alpha

Interferon-A (IFN-A) is an effective agent in the treatment of chronic myelogenous leukemia (CML). Hematologic remissions occur in the majority of patients with newly diagnosed disease, and cytogenetic remissions may occur in up to 50% of patients. Several studies have shown a correlation between the dose of IFN-A and achievement of a major cytogenetic response; this response has also been correlated with prolonged survival. However, IFN-A may be associated with significant side effects that reduce enthusiasm for the use of this drug, produce difficulties in patient compliance, and limit the dose delivered to the patient, thus resulting in ineffective use of IFN-A. Experience with this drug has led to a refinement in techniques for initiation of therapy as well as interventions to deal with side effects. These strategies are often not discussed in publications dealing with response rates and survival. In this review we discuss strategies to minimize toxicity and improve the effectiveness of IFN-A in the treatment of CML.

Interferon-alpha therapy for chronic myelogenous leukemia

PURPOSE

To provide a status report on the use of interferon (IFN)-alpha in patients with chronic myelogenous leukemia (CML).

DATA SOURCES

Data on IFN-alpha therapy for CML collected from published articles identified in a MEDLINE computer search.

RESULTS

Previously untreated patients with low-risk factors and early-stage disease consistently had the best results in clinical trials. A dose response was seen, with patients treated with dosages of 5 million units (MU)/m2 per day showing the greatest incidence of cytogenetic remissions. In addition, randomized trials showed a survival advantage for IFN-alpha-treated patients. In studies comparing IFN-alpha therapy to chemotherapy, IFN-alpha produced significantly more major and durable cytogenetic responses than chemotherapy did. In studies combining IFN-alpha and chemotherapy, patients had significantly more cytogenetic responses, although more patient accrual and follow-up data are needed to offer conclusive statements concerning durability of response. IFN-alpha also showed activity in maintaining remissions after both chemotherapy and bone marrow transplantation.

CONCLUSIONS

IFN-alpha has significant activity in patients with CML, with best results at dosages of 5 MU/m2 per day. At these dosages, in patients with early-stage, Philadelphia+ CML, hematologic response rates of 70% to 80% and cytogenetic response rates of 50% (approximately 20% of which were complete) are seen. One randomized trial shows a survival advantage with cytogenetic response in IFN-alpha-treated patients, and this advantage appears to be unrelated to the degree of that response. These questions remain under study.

Biotherapy of chronic myelogenous leukemia

The aim of this review is to summarize the current knowledge on the clinical results of biotherapy of chronic myelogenous leukemia (CML) and potential mechanisms of the antitumor action of interferon alpha. IFN alpha treatment induces hematologic and cytogenetic remissions in patients with chronic phase CML. In addition, the duration of the chronic phase is prolonged by IFN alpha resulting in a significant survival benefit. In two randomized clinical trials this survival benefit was demonstrated in all chronic phase CML patients independent of their risk scores. Moreover, IFN treatment also delays the onset of clinical relapse after allogeneic bone marrow transplantation. The critical mechanisms of IFN action have not yet been identified. Both direct and indirect antiproliferative mechanisms have been described. In particular, differential regulation of growth promoting and growth inhibiting cytokines represents an attractive hypothetical mechanism of IFN action. Nevertheless, no leukemia specific IFN activities explaining cytogenetic remissions and/or delay of disease progression have been identified. Further research on that field are required to further improve biological CML therapies.