The targeted agent Sprycel® (dasatinib) is an effective treatment for patients newly diagnosed with chronic myeloid leukemia (CML). These results were recently presented at the 2008 annual meeting of the American Society of Clinical Oncology.
CML is a cancer that originates in the immune cells. It affects approximately 4,600 people annually in the United States. 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 properly, leaving patients susceptible to infection.
Chronic myeloid leukemia begins with a chronic phase, during which few or no clinical problems occur. However, when left untreated, the chronic phase progresses into acute phases; these phases, called the accelerated and blastic phases, are characterized by fast-growing and aggressive cancer. Patients reaching these acute phases have a poor prognosis for long-term survival.
Philadelphia chromosome-positive (Ph-positive) CML refers to the majority of cases of CML in which a genetic abnormality, referred to as the Philadelphia chromosome, results in the constantly activated growth of cancer cells. Roughly 30% of adult patients with acute lymphocytic leukemia (ALL) also have this genetic abnormality.
Gleevec® (imatinib mesylate) is a biological agent that binds to and slows or stops the uncontrolled growth of cancer cells with the Philadelphia chromosome genetic mutation. Although Gleevec produces sustained anticancer responses in a significant portion of patients with Ph-positive CML, some patients stop responding to Gleevec or are not able to tolerate Gleevec. Unless these patients undergo a stem cell transplant, treatment options have remained limited.
Sprycel is an agent that is approved for the treatment of patients with CML who have stopped responding to Gleevec and for the treatment of acute lymphoblastic leukemia (ALL). Clinical trials are ongoing to compare novel agents with Gleevec as initial therapy for CML.
Researchers from the M.D. Anderson Cancer Center in Houston, Texas, recently conducted a clinical trial to evaluate Sprycel as initial therapy for patients diagnosed with CML. The trial included 40 patients with newly diagnosed CML who were treated with Sprycel. Results from these patients were compared with data from patients with newly diagnosed CML who had been treated with Gleevec at two doses (400 milligrams per day and 800 milligrams per day). Complete cytogenetic responses (complete disappearances of the Philadelphia chromosome), a marker of disease response, were compared between groups of patients.
The following table summarizes the main findings of this trial to date:
Sprycel was well tolerated; the main side effect was muscle and bone pain. These researchers suggested that Sprycel produced more rapid and possibly more complete cytogenetic responses than 400 milligrams per day of Gleevec; however, a clinical trial that directly compares Sprycel to different doses of Gleevec is necessary to determine the true clinical effectiveness of Sprycel.
Patients with newly diagnosed CML may wish to speak with their physician regarding their individual risks and benefits of participation in a clinical trial evaluating Sprycel and other agents. Information regarding ongoing clinical trials can be found at the National Cancer Institute (www.cancer.gov) and www.eCancerTrials.com.
Reference: Borthakur G, Kantarjian HM, O/Brien SM, et al. Efficacy of dasatinib in patients (pts) with previously untreated chronic myelogenous leukemia (CML) in early chronic phase (CML-CP). Journal of Clinical Oncology. 2008;26:abstract 7013.