People who survive cancer in childhood have a heightened risk of dying of a heart attack, stroke or another cancer decades later — a risk that is likely to be due to the original treatment, scientists said on Tuesday.

A study by British researchers of death rates among almost 18,000 people who survived childhood cancer found that the number of premature deaths among survivors was 11 times the number expected in the general population.

The findings suggest cancer survivors' long-term health is at risk from the treatment they receive in childhood and shows the need to find ways of improving that treatment and ensuring patients have better access to long-term care.

"These findings confirm the importance of very long-term outcome data and that survivors should be able to access health care programs even decades after treatment," said Raoul Reulen of Birmingham University, who led the study.

He said further investigations were important because "any excess mortality may be related to long-term complications of treatment."

A study by doctors from the United States last year found that survivors of childhood cancer are at risk of a range of cardiac problems such as heart failure, heart attacks and heart disease and the risks continued up to 30 years after treatment.

British guidelines on long-term follow-up for cancer survivors recommend routine heart screening only every five years, while in the United States screening is more frequent for those judged to be at greater risk.

Writing in the Journal of the American Medical Association, Reulen said new cancers — known as "second primary cancers" — were a "recognized late complication of childhood cancer.

"This is due largely to exposure to radiation during treatment, and to the side effects of some of the more toxic cancer drugs, he said.

Reulen's team analyzed data from 17,981 people who had survived a childhood cancer for at least five years. They had all been diagnosed before the age of 15 between 1940 and 1991 in Britain and were monitored until the end of 2006.

Survivors experienced 11 times the number of deaths expected from the general population, and although this rate declined over the years, it was still three times higher than expected 45 years after their original diagnosis.

The findings also showed that only 7 percent of the deaths among childhood cancer survivors were due to a recurrence of their original disease, while 77 percent were due to new cancers, heart disease and so-called cerebrovascular disease, which causes high blood pressure and strokes.