ASH 2008: Imatinib Can Be Discontinued in Some Patients With CML

Roxanne Nelson

December 08, 2008

December 8, 2008 (San Francisco, California) — For some patients with chronic myeloid leukemia (CML), it might be possible to discontinue imatinib mesylate (Gleevec) after they have achieved a complete molecular remission. Research presented here at the American Society of Hematology (ASH) 50th Annual Meeting and Exposition confirmed the results of a pilot study that demonstrated that remission can be sustained after imatinib is discontinued, particularly in patients who have been pretreated with interferon.

The discontinuation of imatinib is feasible and does not automatically lead to relapse, reported lead author, François-Xavier Mahon, MD, from Hématopoïèse leucémique, Université Victor Segalen CHU de Bordeaux, in France.

"Imatinib has greatly improved survival in CML," said Dr. Mahon, "but patients must continue on the treatment for an unknown period of time."

Imatinib, a BCR-ABL tyrosine kinase inhibitor, is able to induce a complete cytogenetic response in more than 85% of patients with CML. However, the researchers note that patients with a complete cytogenic response tend to relapse when imatinib is discontinued, and less than 10% of patients achieve a molecular remission, defined by an undetectable residual disease using real-time quantitative–polymerase chain reaction.

Previously, Dr. Mahon and colleagues conducted a pilot study and explored the feasibility of discontinuing imatinib in CML patients who had experienced a complete molecular response. Of the 15 patients included in the cohort, 7 relapsed within 6 months, but they were able to reattain a complete molecular response after imatinib was restarted. The other 8 patients remain in remission after the discontinuation of imatinib (median follow-up is 37 months).

The patients who did not relapse were all pretreated with interferon, Dr. Mahon pointed out.

The current trial looked at 69 patients from 22 centers in France and, of this group, 60 patients had follow-up for more than 1 month. They had a median age of 62 years (range, 32–81 years). Thirty one had been previously treated with interferon, and 29 were de novo. To meet the criteria for inclusion, the patients had to be receiving imatinib treatment and to have had a complete molecular response and undetectable BCR-ABL transcript for at least 2 years.

Currently, 27 patients have relapsed since the discontinuation of their imatinib, and most of the relapses were observed during the first 6 months of discontinuation. Of this group, 13 patients had received interferon and 14 had only received imatinib.

"At 9 months, 46% of patients are still in remission," said Dr. Mahon. "Fifty-three percent were pretreated with interferon and 39% are de novo patients."

Dr. Mahon also emphasized that all of the patients who relapsed were sensitive to imatinib after it was restarted. Some of the relapsed patients went back into remission very quickly, but for others, it is a slower process.

Although the follow-up in this study is short, patients in the pilot study have now been followed for several years. The results from both of these trials confirm that complete molecular response can be sustained after imatinib is discontinued. This is particularly true for patients who have been pretreated with interferon, said Dr. Mahon.

But among the patients who were not pretreated with interferon, over half have not relapsed, and 20% have reached a follow-up of 6 months or more without relapse. Dr. Mahon concluded that it is possible to stop imatinib treatment in patients who have a sustained complete molecular response, even in those who received single-agent treatment with imatinib.

American Society of Hematology (ASH) 50th Annual Meeting and Exposition: Abstract 187. Presented December 8, 2008.

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