NEW YORK (Bloomberg) – Children treated for leukaemia survived more often when radiation therapy to the head was omitted, a study found.

Their five-year survival rate was 93.5 percent in the research published online last week in the New England Journal of Medicine, compared with an average 87.5 percent rate among similar US children with radiation from 2000 to 2004, lead author Ching-Hon Pui said. Tailoring chemotherapy treatment enabled doctors to avoid radiation therapy to the head, a strategy that may prevent long-term side effects including second cancers and hormone imbalances, the researchers said.

Acute lymphoblastic leukaemia is the most common cancer in children younger than 15 years old, according to the National Cancer Institute. About 100 children each year are diagnosed initially with this form of leukaemia in the brain and spine, and hundreds of others with a high-risk form of the disease receive radiation to their brains preventatively, he said.

"We can eliminate a very toxic component of treatment and not only preserve the good outcome from prior trials, but improve upon it," said study author William Evans, chief executive officer of St. Jude Children's Research Hospital in Memphis, Tennessee. "We have better outcomes and less toxicity and that is very encouraging."

Researchers studied 498 patients treated for acute lymphoblastic leukaemia from 2000 to 2007 at St. Jude and at Cook Children's Medical Center in Fort Worth, Texas. Doctors then modified doses of chemotherapy drugs based on each individual child to avoid over-treating or under-treating. They also identified which patients needed more drugs or intensified treatments such as bone marrow transplants. The results showed the overall five-year survival rate was 93.5 percent for the 498 children. "This is the first study that pushes the cure rate to 90 percent – the best ever," said Pui, chair of the oncology department at St. Jude, in an e-mail. "This is the first study that proves that with effective chemotherapy, cranial irradiation can be totally omitted" in children with acute lymphoblastic leukaemia.