High rates of durable response are achieved with imatinib after treatment with interferon alpha plus cytarabine: results from the International Randomized Study of Interferon and STI571 (IRIS) trial.

BACKGROUND: Imatinib is the standard of care for newly diagnosed chronic-phase chronic myeloid leukemia. The largest randomized clinical trial of imatinib was the multinational IRIS trial in which 1106 patients were randomized to receive either imatinib 400 mg/day or a standard regimen of interferon-alpha plus cytarabine. DESIGN AND METHODS: Patients were allowed to cross over to the opposite treatment for intolerance, lack of response, disease progression, and, following release of the initial efficacy data, reluctance to remain on therapy with interferon-alpha plus cytarabine. The safety and efficacy of imatinib in patients who crossed over from interferon-alpha plus cytarabine to imatinib is reported here. RESULTS: Of 553 patients originally assigned to interferon-alpha plus cytarabine, 65% crossed over to imatinib, of whom 67% continue to receive treatment. After a median of 54 months of imatinib treatment on study, 93% achieved complete hematologic remission, 86% achieved major cytogenetic remission, and 81% achieved a complete cytogenetic remission as the best observed response. Estimated rates of freedom from progression to accelerated or blast phase and overall survival were 91% and 89%, respectively, at 48 months after starting imatinib. CONCLUSIONS: This is the largest analysis to date describing the efficacy of imatinib in patients who have received prior therapies for chronic myeloid leukemia and it demonstrates excellent responses to this treatment. (ClinicalTrials.gov identifier: NCT00006343).

The prognosis for patients with chronic myeloid leukemia who have clonal cytogenetic abnormalities in philadelphia chromosome-negative cells.

BACKGROUND: Clonal cytogenetic abnormalities (CCA) were detected in Philadelphia chromosome (Ph)-negative cells in some patients with chronic myeloid leukemia (CML) who attained a cytogenetic response to imatinib mesylate. In some patients, CCA/Ph-negative status was associated with myelodysplasia or acute myeloid leukemia. The objective of the current study was to determine the prognostic impact of CCA/Ph-negative cells. METHODS: The authors compared the pretherapeutic risk factors (Kruskall-Wallis test), exposure to cytotoxic drugs (chi-square test), and overall and progression-free survival (Kaplan-Meyer and logistic regression analysis, respectively) of 515 patients with mostly chronic-phase CML who were treated with imatinib mesylate after failure of interferon-alpha according to whether they attained a major cytogenetic response (MCR) (n = 324 patients), an MCR with CCA/Ph-negative status (n = 30 patients), or no MCR (n = 161 patients). RESULTS: CCA/Ph-negative status most frequently involved chromosomes Y, 8, and 7. No significant differences in pretherapeutic risk factors were detected between patients who attained an MCR with and without CCA/Ph-negative cells, except that exposure to alkylating agents was more frequent in patients with CCA/Ph-negative cells, and overall and progression-free survival were identical. With a median follow-up of 51 months, only 2 patients developed myelodysplastic syndromes (MDS). CONCLUSIONS: The overall prognosis for patients who had CML with CCA/Ph-negative status was good and was driven by the CML response to imatinib mesylate. Isolated CCA/Ph-negative cells in the absence of morphologic evidence of MDS do not justify a change in therapy.

Five-year follow-up of patients receiving imatinib for chronic myeloid leukemia.

BACKGROUND: The cause of chronic myeloid leukemia (CML) is a constitutively active BCR-ABL tyrosine kinase. Imatinib inhibits this kinase, and in a short-term study was superior to interferon alfa plus cytarabine for newly diagnosed CML in the chronic phase. For 5 years, we followed patients with CML who received imatinib as initial therapy. METHODS: We randomly assigned 553 patients to receive imatinib and 553 to receive interferon alfa plus cytarabine and then evaluated them for overall and event-free survival; progression to accelerated-phase CML or blast crisis; hematologic, cytogenetic, and molecular responses; and adverse events. RESULTS: The median follow-up was 60 months. Kaplan-Meier estimates of cumulative best rates of complete cytogenetic response among patients receiving imatinib were 69% by 12 months and 87% by 60 months. An estimated 7% of patients progressed to accelerated-phase CML or blast crisis, and the estimated overall survival of patients who received imatinib as initial therapy was 89% at 60 months. Patients who had a complete cytogenetic response or in whom levels of BCR-ABL transcripts had fallen by at least 3 log had a significantly lower risk of disease progression than did patients without a complete cytogenetic response (P<0.001). Grade 3 or 4 adverse events diminished over time, and there was no clinically significant change in the profile of adverse events. CONCLUSIONS: After 5 years of follow-up, continuous treatment of chronic-phase CML with imatinib as initial therapy was found to induce durable responses in a high proportion of patients. (ClinicalTrials.gov number, NCT00006343 [ClinicalTrials.gov].)

Survival advantage from imatinib compared with the combination interferon-alpha plus cytarabine in chronic-phase chronic myelogenous leukemia: historical comparison between two phase 3 trials.

In the multinational IRIS study comparing imatinib with interferon plus cytarabine (IFN/Ara-C) in patients with newly diagnosed chronic-phase chronic myelogenous leukemia (CP CML), imatinib demonstrated significantly higher rates of complete cytogenetic responses (CCyRs) and improved progression-free survival (PFS). However, because of a high early crossover rate to imatinib, survival benefit was not assessable. Here, we report the result of a study comparing long-term outcome of patients included in 2 prospective randomized trials: 551 patients assigned to imatinib in the IRIS trial from 2000 to 2001 and 325 patients who received the combination IFN/Ara-C in the CML91 trial between 1991 and 1996 before imatinib was available. With a follow-up of 42 months for both groups of patients, estimated CCyR, survival free of transformation, and overall survival were significantly higher with imatinib compared with IFN/Ara-C (P < .001, P = .004, and P < .001, respectively). Improved overall survival was also confirmed within different Sokal prognostic risk groups. Of interest, among all patients who achieved major cytogenetic response or CCyR at 12 months, the survival rate was similar irrespective of their treatment. In conclusion, within the limitation of this historical comparison, there is a survival advantage from first-line therapy with imatinib over IFN/Ara-C.