SURVIVORS OF CHILDHOOD cancer who underwent radiotherapy treatment that exposed their pancreas to radiation may be at higher risk of developing diabetes in later life, according to new research.

As part of the study, more than 2,500 patient medical records and questionnaires relating to British and French people who had suffered childhood cancer but survived for at least 20 years afterwards were analysed. The results of the study, published in the Lancet Oncology, provide the first link between diabetes and radiation.

Using sophisticated mathematical modelling technique, as well as information regarding how the patients was likely to have been treated with radiotherapy at the time, researchers reconstructed exactly how and where patients had been exposed to radiation.

Tail of the pancreas

The results showed that, by the age of 45, 2·3 per cent patients who had not received radiotherapy had been diagnosed with diabetes, compared with 6·6 per cent of those people who had been treated for childhood cancer with radiotherapy.

Researchers found that if the tail of the pancreas had been exposed to radiation during treatment in childhood, patients were significantly more likely to be diagnosed with diabetes later in life.

Radiation exposure to other parts of the pancreas did not affect diabetes rates which, the authors speculate, may be because the tail of the pancreas contains a type of cell involved in insulin production.

The data also indicated a link between high doses of radiation and a higher risk of developing diabetes in later life, as patients who had received an average radiation dose of 24·2 Grays to the tail of the pancreas being 12·6 times more likely to be diagnosed with diabetes within 20 years of completing radiation therapy, compared to patients who did not receive radiation therapy. (A Gray (Gy) is the SI-derived unit for absorbed radiation dose; one Gray is equal to an absorbed dose of 1 Joule of energy per kilogram.)

Cancer type

Researchers also found that the type of cancer a patient had suffered affected later diabetes risk, with kidney cancer increasing the likelihood of a patient later developing diabetes. Some 14·7 per cent of patients who had been treated for nephroblastoma (kidney cancer) had been diagnosed with diabetes by age 45, compared to an average of 3·1 per cent for other types of cancer included in the study.

Radiotherapy treatment for kidney cancer is likely to increase the likelihood of the tail of the pancreas will be exposed to radiation, as therapy for nephroblastoma often focuses in the abdominal area, researchers said.

One of the authors of the paper, Dr Florent de Vathaire of the Centre for Epidemiology and Public Health (CESP) of INSERM at the Gustave Roussy Institute in France, said the findings underlined the importance of the pancreas being “regarded as a critical organ” when planning radiation therapy, particularly in children.

Radiation therapy guidelines

“Until now, the pancreas was one of the few organs not considered at risk of normal tissue complication in the French and the UK national guidelines for cancer radiation therapy. 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,” she said.

Kevin Oeffinger of the Memorial Sloan-Kettering Cancer Center, New York, agreed that the clinical implications of this study were important, as radiation remains an integral part of therapy for many children with Wilms’ tumour (a type of kidney cancer) or neuroblastoma.

“Diabetes is a major risk factor for all-cause and cardiovascular mortality. Further study is therefore needed to clarify the mechanisms underlying diabetes after abdominal radiation. Understanding these mechanisms will, hopefully, result in the development of targeted interventions that will lead to a reduction in risk in this population.”

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