Childhood cancer survivors likely to be diabetic later in life

Childhood cancer survivors likely to be diabetic later in life

Childhood cancer survivors, who underwent radiotherapy exposing their pancreas to radiation at a formative stage,are at higher risk of developing diabetes later in life, said a report by French researchers in an article to be published in The Lancet Oncology on Friday.

The study, which analysed more than 2,500 patient questionnaires and medical records from French and British people who had cancer in childhood and survived for at least 20 years after undergoing treatment, is the first to link diabetes and radiation.

Researchers used sophisticated mathematical modelling techniques to reconstruct how and where the respondents were exposed to radiation.

At the age 45,2.3 per cent patients who had not received radiotherapy had been diagnosed with diabetes, compared with 6.6 per cent of those treated for childhood cancer with radiotherapy. Researchers discovered that when the tail of the pancreas was exposed to radiation,patients were significantly more likely to be diagnosed with diabetes later in life. This could be because of the presence of pancreatic beta cells in the tail which are known to be the primary secretion source of insulin.

They found that higher doses of radiation resulted in a greater likelihood of acquiring diabetes later in life,with patients who received an average radiation dose of 24.2 Gray to the tail of pancreas being 12.6 times more likely to be diabetic within 20 years of completing radiation therapy, compared those who didn’t receive radiation.

Dr Florent de Vathaire of the Centre for Epidemiology and Public Health at Gustave Roussy Institute in France, one of the authors of the paper,said: “The pancreas needs to be regarded as a critical organ when planning radiation therapy, particularly in children. 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 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.”

Contouring refers to marking of outlines of vital organs on the skin so that these areas are avoided during radiotherapy.

Opinion is divided on the matter among Indian doctors. Dr P K Julka, professor in the AIIMS’s department of radiotherapy,says the intensity of radiation specified in the study is too high.

“We do not give 24 Gray radiation in cases of Wilms tumour. It is clear that higher the dosage, greater is the likelihood of diabetes in later life so we usually limit it to 10-12 Gray.”

“I agree with the results of the study because the toxicity of radiotherapy increases with the passage of time and the damage to the pancreatic cells will also develop as time passes. The important message is for radiation oncologists that the tail of pancreas should not be included in the radiation field when irradiating abdominal tissues,” says Dr Shyam Aggarwal, consultant oncologist at Sir Ganga Ram Hospital.