Some childhood cancer survivors who were treated with radiation to the abdomen may be at higher risk for diabetes, European research suggests.
Children with cancer who are treated with radiation are closely monitored for complications but the pancreas was not considered at risk, say British and French researchers.
They combed through the medical records of 2,520 people in both countries who had a solid cancer or lymphoma, excluding leukemia, and who survived for at least 20 years after treatment. Investigators also sent questionnaires to patients and their doctors.
At age 45, 6.6 per cent of those who'd received radiation had been diagnosed with diabetes compared with 2.3 per cent among those who had not received radiation, the researchers said in this week's issue of the medical journal the Lancet.
"Our findings indicate that the pancreas is an organ at risk during radiation therapy and has to be contoured when planning treatment, to ensure a radiation dose of as low as possible," Dr. Florent de Vathaire of the Centre for Epidemiology and Public Health at INSERM in France and his co-authors concluded.
"Our findings emphasize the need to test for glucose tolerance in all patients with a history of abdominal radiation therapy to enable the early detection of diabetes."
When the researchers modeled how the radiation was given, they found that the risk of diabetes increased strongly with radiation dose to the tail of the pancreas. That's where the islets of Langerhans are concentrated, which are involved in producing insulin.
The results were the same after taking adult body mass index into account.
Higher doses of radiation to the tail of the pancreas resulted in a greater chance of developing diabetes in later life.
The researchers noted that radiation therapy techniques have changed since the study began in 1986 and the findings may not apply to children treated more recently.
"The clinical implications of this study are important, since radiation remains an integral part of therapy for many children with Wilms' tumour or neuroblastoma," Dr. Kevin Oeffinger and Dr. Charles Sklar of the pediatrics department at Memorial Sloan-Kettering Cancer Center in New York wrote in a journal commentary published with the study.
The commentators said the large size, confirmation of diabetes by the survivors' physicians and radiation dose estimates for different regions of the pancreas were strengths of the study.
Oeffinger and Sklar said the main weakness was the lack of lab testing to probe the insulin resistance more precisely.
The study was independent of any pharmaceutical company or other commercial interests.