Benefit of Imatinib in Chronic Myeloid Leukemia Persists Long Term in IRIS Trial


Key Points

  • Treatment with imatinib was associated with an estimated 10-year overall survival of 83% in patients with CML.
  • Long-term follow-up has revealed no new safety signals.

Long-term follow-up of patients with chronic myeloid leukemia (CML) randomized to imatinib in the IRIS trial was reported by Hochhaus et al in The New England Journal of Medicine.

In the open-label crossover-design trial, 1,106 patients with CML were randomized to receive imatinib at 400 mg/d (n = 553) or interferon alfa plus cytarabine (n = 553). The first patient was enrolled in June, and the last visit of the last patient was in January 2012.

At 18 months, imatinib treatment was associated with a complete cytogenetic response rate of 76.2%, compared with 14.5% with interferon alfa plus cytarabine; as a result of the early outcomes, a total of 65.6% of the original interferon alfa plus cytarabine group crossed over to imatinib at a median of 0.8 years, limiting further efficacy comparisons. As noted by the authors: “This trial fundamentally changed CML treatment and led to marked improvements in prognosis for patients.”

Long-Term Outcomes

Median follow-up for the current report was 10.9 years. Estimated 10-year overall survival in the imatinib group was 83.3%; 260 patients (47.0%) were alive and still receiving imatinib at 10 years, 96 patients (17.4%) were alive and not receiving imatinib, there were 86 known deaths (15.6%), and 111 patients (20.1%) had an unknown survival status. Overall, 48.3% of the group completed study treatment through study closure in 2011 to 2012, and 82.8% had a complete cytogenetic response.

A total of 51 patients (9.3%) had a serious adverse event considered related to study treatment; of them, the most common was abdominal pain (4 patients, 0.7%). Drug-related serious adverse events were most common during the first year of treatment and subsequently declined in frequency. Cardiac serious adverse events irrespective of causal attribution occurred in 39 patients (7.1%), and serious adverse events consisting of a second benign or malignant neoplasm occurred in 62 patients (11.3%).

The authors concluded: “Almost 11 years of follow-up showed that the efficacy of imatinib persisted over time and that long-term administration of imatinib was not associated with unacceptable cumulative or late toxic effects.”

The study was funded by Novartis Pharmaceuticals.

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