Phase 2 study results of targeted therapy added to chemo
Results of a phase two clinical trial published October 5th in the Journal of Clinical Oncology show that adding continuous daily doses of a targeted drug called imatinib mesylate to regular chemotherapy more than doubled three-year survival rates for children with a high risk type of blood cancer called Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL).
The Children's Oncology Group performed the study at nearly 20 North American centres under the leadership of Dr. Kirk Schultz, head of childhood cancer research at the Child & Family Research Institute (CFRI) and a pediatric oncologist at BC Children's Hospital, an agency of the Provincial Health Services Authority.
"With conventional chemotherapy, the three-year survival rate for children with this high-risk type of leukemia is between 30-35 per cent," says Dr. Kirk Schultz, professor of pediatrics at the University of British Columbia.
"Adding continuous exposure to imatinib for two-and-a-half years made a big difference and increased the survival rates to 87 per cent. The drug was well tolerated and it didn't have any significant side effects," he says. Survival rate refers to the length of time that a patient survived without a relapse and without developing a new cancer.
There are multiple types of acute lymphoblastic leukemia and each responds differently to treatment. Ph+ ALL involves genetic abnormalities on two specific chromosomes.
Because traditional chemotherapy doesn't work well for many children with Ph+ ALL, the standard treatment is blood and marrow transplantation, a life-saving procedure that's associated with a risk of complications.
"By using the targeted drug imatinib in combination with traditional chemotherapy, these results suggest that we've been able to improve survival enough that we may no longer have to do blood and marrow transplants for this disease," says Dr. Schultz. "Understanding more about the genetics of cancers allows us to determine the best way to treat each child and be more selective in the appropriate use of expensive medications."
Known commercially as Gleevec-, imatinib is a pill that's used to treat some adult leukemias and gastrointestinal cancers. It binds to a specific protein in cancer cells and prevents the cells from proliferating.
Collaborative networks such as the Children's Oncology Group are crucial for recruiting sufficient numbers of patients to trial new treatments for rare diseases such as Ph+ ALL, which is diagnosed in approximately six children and 90 adults each year in Canada.