Scientists have developed a formal method for estimating the number of children diagnosed with leukaemia in the UK who are cured – meaning they have no greater risk of dying prematurely than children who never had leukaemia.

The cure rate has increased from 25 per cent in the early 1970s to 68 per cent in the early 1990s – and this figure is predicted to rise to 73 per cent for children diagnosed more recently.

The success of leukaemia treatment has previously been judged on five-year survival rates, which increased from 33 per cent to 79 per cent during 1971-2000. For some types of leukaemia, five-year survival is as high as 83 per cent.

The team examined how survival has changed over the years and they defined 'cure' as the point when the life expectancy of children diagnosed with leukaemia returned to normal for their age and sex.

First author Dr Anjali Shah, from the London School of Hygiene and Tropical Medicine, whose study was funded by charity CHILDREN with LEUKAEMIA said: "It's great that children diagnosed with leukaemia can be told that the numbers cured of this terrible disease are increasing.

"We think the substantial increase in survival and 'cure' is largely due to improvements in treatment and care, which have come about thanks to international research collaboration and well-organised, multi-disciplinary trials – many of which have been led by researchers in Britain. Some survivors still experience adverse effects years after the end of treatment, which emphasises the need for long-term medical surveillance of these people."

The research is based on data from the National Registry of Childhood Tumours, which holds statistics on virtually all children under the age of 15 diagnosed with cancer in Great Britain.

Senior author Professor Michel Coleman, who leads the Cancer Research UK Cancer Survival Group at the London School of Hygiene and Tropical Medicine, said: "Our study suggests that the development of new treatments for leukaemia, combined with clinical trials to refine treatment strategies, has been effective in curing more children with leukaemia.

"But alongside the more intensive treatments for leukaemia that increase the chance of cure, we need to reduce the risk of longer-term adverse effects that children may suffer in later life, which can include recurrence of cancer in other parts of the body."

Edward Copisarow, chief executive of CHILDREN with LEUKEAMIA, said: "The research makes an important contribution to the way the success of childhood leukaemia treatment is evaluated. This is the first time that anyone has estimated childhood leukaemia cure trends over time. Estimating cure and determining for how long patients should be monitored is a valuable step beyond the arbitrary success measures of survival 5 or 10 years after diagnosis, because it provides a better sense of the long-term success we are having in fighting this disease."

Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "Although the majority of children with leukaemia can be cured, around a third don't respond well to current treatments and our efforts must focus on finding new treatments so that every child can survive a diagnosis of this disease.

"We will also need to continue long-term monitoring of childhood leukaemia survivors to document any effects the treatment may have in later life. This will help doctors to improve treatments for future patients."