Using a targeted cancer drug more than doubled survival rates among children with a rare type of leukemia, a B.C. researcher has found.

The cancer is called Philadelphia chromosome-positive acute lymphoblastic leukemia, or Ph+ALL. About one out of five adults with ALL and a small number of children have this type, according to the Leukemia & Lymphoma Society.

The disease is usually treated with marrow transplants and chemotherapy, but relapse rates are high.

A combination of chemotherapy with imatinib, known commercially as Gleevec — a drug that targets the specific chromosomes affected in Ph+ALL — improved three-year survival rates from 35 per cent before the targeted drug was used to 87 per cent afterward for those who took it for more than 280 days.

The survival rate is a measure of how long a patient survives without a relapse and without developing a new cancer.

Genetics of cancer

Pediatric oncologist Dr. Kirk Schultz of the BC Children's Hospital led the study at nearly 20 centres across North America.

"Blood and marrow transplant is used as the preferred treatment for patients who we don't have a very good chance of curing, such as the Philadelphia chromosome acute lymphoblastic leukemia, the type that was used in this trial," Schultz said in an interview from Washington on Tuesday.

"So now that this type of chemotherapy regimen has come out, we no longer will need to go to transplant as our first and really last option."

History of Gleevec

Imatinib mesylate, also called Gleevec, was developed about 10 years ago by Brian Druker of Oregon Health & Science University and Nicholas Lydon, formerly of Novartis AG, the company that produces the leukemia drug.

The drug targets mutations in specific chromosomes and cancer types.

This class of drugs is given with chemotherapy.

People who received the drug for 42 and 63 days had the same survival rates as current standard treatments, the team found.

The drug is administered as a pill used to treat some adult leukemias and gastrointestinal cancers. It binds to a certain protein in cancer cells and prevents them from growing.

The results were submitted for publication early because they seemed so promising.

Schultz is planning followup studies to get five-year survival data, and to test whether the combination therapy should replace blood and marrow transplants as the standard treatment for the disease.

Results of the Phase 2 trial were published Oct. 5 in the Journal of Clinical Oncology.

The study was funded by the National Cancer Institute of the U.S. National Institutes of Health.