A long-term study of patients with chronic myeloid leukemia (CML) indicated that the targeted therapy drug imatinib is the treatment of choice for those who do not respond to interferon alpha therapy.

As noted in a statement announcing the study findings, which were reported in the journal Cancer, the kinase inhibitor imatinib is now the standard drug administered after a diagnosis of CML. Up to 93% of persons who use it as initial therapy for the disease survive at least 8 years, compared with an average survival of only 3 to 6 years before imatinib was approved for CML treatment in 2001. However, approximately 15,000 to 20,000 patients in the United States may have started taking imatinib only after failing to respond to interferon, a biological response modifier that previously served as the standard drug for CML.

A team led by Hagop Kantarjian, MD, of the University of Texas MD Anderson Cancer Center in Houston, conducted an analysis of 368 people with chronic phase CML who did not respond to interferon. A total of 247 (67%) patients achieved a complete cytogenetic response after being switched to imatinib. Of the 327 patients further evaluated, 207 (63%) achieved a major molecular response.

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The estimated 10-year survival rate was 68%, compared with estimates of 20% to 30% yielded by previous research involving patients who did not respond to interferon therapy and did not have access to imatinib.

In the current study, the progression-free survival rate was 67% and the event-free survival rate was 51%. Factors with an independent negative effect on survival included age of 60 years or older, a hemoglobin level of less than 10 g/dL, bone marrow basophils of 5% or more, any peripheral blasts, and colonal evolution. The estimated 7-year survival rate according to the presence of no factors was 93%; 1 or 2 factors, 70%; and 3 or more factors, 25%.

According to the authors, these findings suggest that most patients can benefit from imatinib after unsuccessful interferon treatments, and other therapeutic options need not be considered.