Some leukemia patients may be able to safely stop treatment

The trials showed that when doctors stopped treating chronic myeloid leukemia (CML) patients with the standard drug imatinib (also called Glivec) some remained completely free of the disease two years later. This contradicts the prevalent belief the treatment should be continued for life because the leukemia would always return if treatment was stopped due to the presence of leukemia-initiating stem cells resistant to imatinib.

The research team, led by Professor François-Xavier Mahon of the Victor Segalen Bordeaux University in France, aimed to find out if treatment with imatinib for CML could be safely discontinued, since little research on this had been done and the drug treatment is expensive. Their study, called the Stop Imatinib (STIM) study, was a prospective, non-randomized trial of 69 CML patients at 19 medical institutions in France. All participants had been taking imatinib for at least two years and were in stable "complete molecular remission" (CMR).

The results were that of the 69 patients followed for at least 12 months, 42 patients (61 percent) relapsed, with 40 of them relapsing in the first six months. The remaining patients did not suffer relapse in the two years they were followed. Imatinib treatment was reinstated for all patients who relapsed and all of them responded well.

The researchers concluded the results of this interim study suggest if patients have been in remission for at least two years it may be possible to discontinue the drug safely, and some patients will remain in remission, effectively having been cured by the drug. The results also suggest a better prognosis can be expected for male patients who have been treated for a long period with imatinib and who have a low prognostic Sokal score. Longer-term studies are continuing.

Chronic myeloid leukemia is a slow-developing form of leukemia. The majority of people with CML have a genetic abnormality in their blood cells called the Philadelphia (Ph) chromosome, which causes the production of an enzyme called tyrosine kinase. The enzyme produces an abnormal protein called BCR/ABL. Imatinib, a tyrosine-kinase inhibitor, is a standard drug for the disease but does not often produce complete remission. For this reason the option of discontinuing imatinib will only apply to around 10 percent of CML patients.

The paper was published online in the journal The Lancet Oncology and will appear in the print version of the journal.

More information: Discontinuation of imatinib in patients with chronic myeloid leukaemia who have maintained complete molecular remission for at least 2 years: the prospective, multicentre Stop Imatinib (STIM) trial, The Lancet Oncology, Early Online Publication, 20 October 2010. doi:10.1016/S1470-2045(10)70233-3

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