Sprycel® (dasatinib) produces a higher response rate and improves progression-free survival in patients with chronic myeloid leukemia (CML) who have grown resistant to Gleevec® (imatinib), according to the results of a study published early online in Cancer.
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.
Sprycel is an oral, targeted 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). Researchers affiliated with the START-R trial have recently completed two years of follow-up of a randomized Phase II study comparing Sprycel and Gleevec in patients with chronic phase CML (CP-CML). The study included 150 patients with Gleevec-resistant CP-CML who were randomized to receive Sprycel or high-dose Gleevec. These patients had shown resistance to the standard dose of 400-600 mg of Gleevec; a dose of 800 mg of Gleevec is considered to be high-dose.
With a minimum follow-up of two years, patients who received Sprycel experienced a higher rate of complete response (93% compared with 82% for the Gleevec group). Furthermore, 53% of patients in the Sprycel group experienced a major cytogenetic response compared with 33% in the Gleevec group, and 44% of patients in the Sprycel group experienced a complete cytogenetic response compared with 18% in the Gleevec group. Also, a major molecular response was observed in 29% of patients receiving Sprycel compared with 12% of patients receiving Gleevec.
The researchers concluded that Sprycel improved the rates of response and progression-free survival compared with Gleevec in patients with CP-CML. Patients who have developed a resistance to Gleevec may benefit from Sprycel.
 Kantarjian H, Pasquini R, Levy V, et al. Dasatinib or high-dose imatinib for chronic-phase chronic myeloid leukemia resistant to imatinib at a dose of 400 to 600 milligrams daily: Two-year follow-up of a randomized phase 2 study (START-R). Cancer [early online publication]. June 17, 2009. DOI: 10.1002/cncr.24504.