Cancer patients who underwent
radiation therapy as children are at greater risk of developing
diabetes later in life, a finding that should prompt changes in
treatment guidelines, French and British researchers said.
By age 45, 6.6 percent of those who had received radiation
were diagnosed with diabetes, in which the body lacks or becomes
resistant to the hormone insulin, according to the survey of
more than 2,500 patients. That compared with 2.3 percent of
those who hadn't had radiation. The higher the dose, the more
likely the children were to develop diabetes, the researchers
wrote in The Lancet medical journal today.
About four out of 10 people with cancer have radiation
therapy, or high-energy X-rays intended to destroy tumors,
according to the U.K.'s National Health Service. When exposed to
radiation, cells in the tail of the pancreas responsible for
insulin production may be damaged, which probably accounts for
the higher incidence of diabetes, the researchers said.
"The pancreas needs to be regarded as a critical organ
when planning radiation therapy, particularly in children,"
said Florent de Vathaire from the Center for Epidemiology and
Public Health at the Gustave Roussy Institute in France, an
author of the research, in an e-mailed statement.
Lack of Insulin
Diabetes, caused by a lack of insulin needed to convert
blood sugar into energy, rarely causes death, though it can lead
to life-threatening complications such as kidney damage and
cardiovascular disease. The condition can be managed through a
combination of dietary control, drug therapy and insulin
injections.
Any potential increase in cases raises important public
health questions at a time when diabetes cases are rapidly
rising around the world, the researchers said. About 366 million
people had the illness last year, according to estimates by the
International Diabetes Federation. That number will probably
increase to 552 million by 2030, caused by an aging population
and lifestyle changes in poorer countries, according to the
group.
The British and French researchers surveyed childhood
cancer patients at least 20 years after their treatment. The
scientists then used mathematical models and information about
radiation therapy at the time of treatment to reconstruct how
patients were exposed to radiation. Childhood cancer survivors
undergoing treatment before the age of 2 were most sensitive to
radiotherapy, the study found.
Kidney Cancer
Children with kidney cancer were most at risk of developing
diabetes, with 14.7 percent of those treated with radiation
diagnosed with the condition by age 45, the study found. That's
probably because the radiation treatment was focused on the
abdominal area, which includes the pancreas, the researchers
said.
Before the study, the effect of cancer treatment on the
pancreas was largely unknown, said Kevin Oeffinger, director of
the adult long-term follow-up program at Memorial Sloan-
Kettering Cancer Center in New York, in a comment accompanying
the article in The Lancet.
"The clinical implications of this study are important,
since radiation remains an integral part of therapy for many
children" with kidney cancer, Oeffinger wrote. "Further study
is needed to clarify the mechanisms underlying diabetes after
abdominal radiation."
Although the precise causes of the association remain
unknown, the findings suggest that radiation therapy targeting
the pancreas should be at the lowest intensity possible, said de
Vathaire.
To contact the reporter on this story:
Mehreen Khan in London at
mkhan108@bloomberg.net
To contact the editor responsible for this story:
Phil Serafino at
pserafino@bloomberg.net
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