According to updated study results presented at the 47th annual meeting of the American Society of Hematology (ASH), Gleevec® (imatinib mesylate) produces good long-term results when used for initial treatment of chronic-phase chronic myeloid leukemia (CML).
Chronic myeloid leukemia (CML), also called chronic granulocytic leukemia, is a cancer that originates in the immune cells. It affects approximately 4,600 people annually in the U.S.
In the case of CML, large numbers of young immune cells do not mature, resulting in an excess accumulation of these cells. These leukemia cells then crowd the bone marrow and blood, suppressing formation and function of other blood cells normally present in these areas. In addition, the leukemia cells cannot perform their function in the body properly, leaving patients susceptible to infection.
Chronic myeloid leukemia begins with a chronic phase, during which few clinical problems, if any, occur. However, when left untreated, the chronic phase progresses into acute phases; these phases are characterized by fast-growing and aggressive cancer and are called the accelerated and blastic phases. Patients reaching these acute phases have a poor prognosis for long-term survival.
Historically, the only curative option for patients with CML was an allogeneic stem cell transplant. However, treatment-related mortality, as well as side effects, can be substantial in patients undergoing an allogeneic stem cell transplant; researchers have thus focused efforts on curative treatment options that are more easily tolerated. Philadelphia chromosome-positive CML refers to the majority of cases of CML in which a genetic abnormality, referred to as the Philadelphia chromosome, results in constantly activated growth of cancer cells. Gleevec is a biological agent that binds to and slows or stops the uncontrolled growth of cancer cells with this genetic mutation. In addition, Gleevec has activity in several biological pathways implicated in the development and/or expression of cancer. An advantage of Gleevec over interferon alfa, another drug used to treat CML, is that Gleevec produces few side effects
To compare Gleevec to interferon as the initial therapy for patients with newly diagnosed chronic-phase CML, an international group of researchers conducted a clinical trial in which 553 patients were assigned to receive Gleevec, and 553 were assigned to receive interferon. After 42 months of follow-up, 75% of the Gleevec patients remained on treatment, compared to only 4% of the interferon patients. The updated study results focus on the Gleevec patients.
Among patients treated with Gleevec, overall survival at 54 months was 90%. Survival varied by Sokal risk score (a tool to estimate CML prognosis); rates of survival ranged from 81% among patients with high-risk CML to 94% among patients with low-risk CML. Response to Gleevec played an important role in survival: Among patients with a complete cytogenetic response to Gleevec (complete disappearance of abnormal cells), survival was excellent among all Sokal risk groups. Among those with a complete cytogenetic response, survival ranged from 90% among those with high-risk CML to 97% among those with low-risk CML.
These updated results confirm that patients with chronic-phase CML who respond to Gleevec have good long-term outcomes. Other work by these researchers suggests that of the roughly 40% of patients who have a significant response to Gleevec after one year, many will continue to show a response after four years.
References: Simonsson B. On behalf of the IRIS Study Group. Beneficial effects of cytogenetic and molecular response on long-term outcome in patients with newly diagnosed chronic myeloid leukemia in chronic phase (CML-CP) treated with imatinib (IM): Update from the Iris Study. Blood . 2005;106:52a. Abstract # 166.
Goldman JM, Hughes T, Radich J, et al. Continuing reduction in level of residual disease after 4 years in patients with CML in chronic phase responding to first-line imatinib (IM) in the IRIS study. Blood . 2005;106:51a. Abstract # 163.
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