Second-Line Drug Successful in Leukemia
CancerWise - July 2007
Early results of an ongoing clinical trial show that the drug dasatinib (Sprycel®) has high response rates as an experimental first therapy for patients newly diagnosed with chronic myelogenous leukemia (CML).
Significance of results
Dasatinib is an established second-line drug treatment for CML, meaning that patients receive it only if they have not responded to imatinib (Gleevec®), the standard treatment drug. This study is showing that dasatinib may be an effective experimental first-line treatment as well.
"Our hypothesis is that treating with dasatinib first will produce an earlier response, which may translate to a better overall survival," says Ehab Atallah, M.D., lead author on the Phase II study and a fellow in M. D. Anderson's Department of Leukemia. "We haven't proved that here, but these early results are encouraging."
Dasatinib was approved in 2006 by the U.S. Food and Drug Administration for patients whose disease is unresponsive to or becomes resistant to imatinib.
Both drugs bind to and block a genetically flawed protein known as BCR-ABL, which causes CML. Dasatinib blocks both forms of BCR-ABL, while imatinib only blocks one.
Imatinib was the first drug to target BCR-ABL. Before its introduction, the median five-year survival rate for CML patients was 50%. Researchers reported last year that the five-year survival rate of patients taking imatinib is 95%.
Researchers are continuing to enroll participants in the study and hope to recruit 100 patients.
Each patient receives a dasatinib dose of either:
- 100 mg once daily
- 50 mg twice daily
So far, researchers have evaluated 35 patients who took dasatinib for at least three months between November 2005 and December 2006.
"Patients taking dasatinib have achieved a complete cytogenetic response (absence of the mutated protein that drives this disease) more rapidly than we've observed historically using the current front-line therapy," Atallah says.
Atallah and lead researcher Jorge Cortes, M.D., a professor in M. D. Anderson’s Department of Leukemia, found that a complete cytogenetic response was achieved in:
- 77% of patients at three months
- 92% of patients at six months
- 95% of patients at 12 months
This rapid response compares favorably to data on M. D. Anderson patients who took imatinib as a first therapy.
Imatinib's complete response rates at six months are:
- 54% at 400 mg daily
- 85% at 800 mg daily
Imatinib's complete response rates at 12 months are:
- 72% at 400 mg
- 92% at 800 mg
To be considered for enrollment in the dasatinib study, patients must have a diagnosis of Ph-positive or BCR-positive CML in the early chronic phase (diagnosed less than a year before). They must have received no therapy or minimal prior therapy.
Possible side effects
Dasatinib's possible side effects, which are usually low-grade, include nausea, skin rash and fluid retention, Attalah says. Occasionally low blood counts may cause infection, bleeding or fatigue. In this study, 15 patients were uncomfortable enough to stop treatment temporarily, but all eventually returned to treatment.
For more information or to participate in this study (protocol 2005-0422), call askMDAnderson at 1-877-632-6789.
CancerWise - July 2007
- MRI Test Improves Woman's Destiny
- Q&A: MRI Needed for High-Risk Breast Cancer
- Test Your Knowledge About Sunscreen
- African-American Breast Cancer Survival Lags
- Shark Cartilage Shows No Benefit in Lung Cancer
- Second-Line Drug Successful in Leukemia
- Cancer Center's 'Front Door' Is askMDAnderson
- Journaling Benefits Cancer Patients, Caregivers