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Adapted from the NCI Cancer Bulletin, vol. 4/no. 16, May 1, 2007 (see the current issue ³).

Investigators enrolled 42 patients with lymphoid blast crisis (LBC) and 74 patients with myeloid blast crisis (MBC) into two separate but identical trials (see the protocol summaries for CA180-006 ⁵ and CA180-015 ⁶). All patients were either resistant to or intolerant of imatinib ⁷, a small-molecule inhibitor used in first-line therapy of CML. Patients received a starting dose of 70 mg of dasatinib twice daily, which could be escalated after four weeks. Dose reductions or interruptions were allowed in response to side effects.

Patients received dasatinib until disease progression despite dose escalation, intolerable toxicity, or withdrawal from the study. Among patients with MBC, 32 percent had a major hematologic response at six months of follow-up; this number rose to 34 percent after eight months. Among patients with LBC, 31 percent had a major hematologic response at both six and eight months of follow-up. Twenty-seven percent of MBC patients and 43 percent of LBC patients had a complete cytogenetic response. Only 11 percent of patients with MBC and two percent of patients with LBC had to discontinue therapy because of side effects.

"Our results indicated that dasatinib represents a potentially important new therapeutic option for patients with imatinib-resistant or imatinib-intolerant MBC-CML or LBC-CML and will undoubtedly affect the treatment paradigm for CML," concluded the authors.

Glossary Terms

Initial treatment used to reduce a cancer. First-line therapy is followed by other treatments, such as chemotherapy, radiation therapy, and hormone therapy to get rid of cancer that remains. Also called induction therapy, primary therapy, and primary treatment.

Referring to lymphocytes, a type of white blood cell. Also refers to tissue in which lymphocytes develop.

Having to do with or resembling the bone marrow. May also refer to certain types of hematopoietic (blood-forming) cells found in the bone marrow. Sometimes used as a synonym for myelogenous; for example, acute myeloid leukemia and acute myelogenous leukemia are the same disease.

A study to compare the results of people taking a new treatment with the results of people taking the standard treatment (for example, which group has better survival rates or fewer side effects). In most cases, studies move into phase III only after a treatment seems to work in phases I and II. Phase III trials may include hundreds of people.