Childhood cancer survival has improved in many countries for two common types of leukemia, a new study has found — progress that experts credit to strengths in cancer care.

In a study published Tuesday in The Lancet Haematology, researchers looked at global childhood cancer incidence data from nearly 90,000 children in 53 countries. They compared the effects of national health-care systems in treating cancer between 1995 and 2009.

"The study shows that the probability that children survive at least five years after diagnosis has increased in most countries for the two most common types of childhood leukemia," said lead author Dr. Audrey Bonaventure, of the London School of Hygiene & Tropical Medicine, U.K.

Those types are acute myeloid leukemia and acute lymphoblastic leukemia.

In Canada, the five-year survival rate for acute lymphoblastic leukemia (ALL) sits at 90.6 per cent. 

The vast majority of children diagnosed with the disease will be cured because it rarely recurs, said Dr. Paul Grundy, the expert lead for pediatrics at the Canadian Partnership Against Cancer.

Grundy was not involved in the research but the partnership helped to fund the study, called CONCORD-2.

"In 1960, the survival was zero. There was no treatment. Children lived for a month or two after diagnosis and died," Grundy told CBC News. "In all of medicine, I think this is one of the top success stories: in just 50 years, to go from zero to 90 per cent survival."

For families, it still means one in 10 will lose their child after a devastating diagnosis, said Grundy, who is also a pediatric hematology oncologist in Edmonton.

He added that in North America, one area for improvement surrounds the long-term side-effects of treatment, which can pose a challenge to how children learn.

The treatment for ALL generally last between two-and-a-half to three years.

'Immense' cause question

In other high-income countries, such as those in Europe, the five-year survival rate for ALL for those 14 and under is also around 90 per cent. But in some regions of Colombia and Thailand, it's still below 60 per cent, Bonaventure said.

"Most leukemias in children are treatable, so these inequalities reflect the lack of access in many countries to optimal treatment and early diagnosis," she said.

In Canada, more intensive treatments are now reserved for children with lower chances of being cured, Grundy said. This includes infants under the age of one. Doctors and researchers now recognize that leukemia cells in these youngest children often have a specific gene mutation that makes them more resistant to treatment.

But how to prevent childhood cancer remains unclear.

"Our ignorance on the causes of childhood cancers is still immense," Dr. Philippe Autier, of the University of Strathclyde Institute of Global Public Health Prevention Research Institute in France, said in an accompanying journal commentary. 

The researchers next plan to update the worldwide trends up to 2014, and to include two other types of childhood cancer — brain tumours and lymphomas — as well as many other cancers in adults.

With files from Amina Zafar