(ChemotherapyAdvisor) – Children and young adults who receive cancer radiotherapy face an increased risk of subsequently developing diabetes, according to a new study by British and French researchers, published in The Lancet.

“The pancreas needs to be regarded as a critical organ when planning radiation therapy, particularly in children,” reported lead author Florent de Vathaire, PhD, Radiation Epidemiology Group, INSERM, Villejuif, France, and coauthors.

Diabetes risk was nonlinearly dose-dependent, they found.  

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“The risk of diabetes increased strongly with radiation dose to the tail of the pancreas, where the islets of Langerhans are concentrated up to 20-29 Gy and then reached a plateau for higher radiation doses,” the team wrote.

Pediatric kidney cancer patients who received radiotherapy were found to have a particularly high 14.7% risk of developing diabetes by middle-age. Overall, childhood radiotherapy patients have a 6.6% risk of developing diabetes by age 45 years.

The relative risk of diabetes per 1 Gy of irradiation to the tail of the pancreas was 1.61 (95% confidence intervals [CIs], 1.21 – 2.68). Patients who had received 10 Gy or more of irradiation to the tail of the pancreas were 11.5 times as likely to develop diabetes as patients who did not receive radiotherapy (RR = 11.5, 95% CI, 3.9 – 34.0). The associations remained statistically significant after statistical adjustment for body-mass index, which was independently associated with diabetes risk (P < 0.0001).

An age-dependent radiosensitivity effect was also noted, with the relative risk of subsequent diabetes per 1 Gy of irradiation being significantly higher for those who received radiotherapy at age 2 years or younger than among older patients (relative risk at 1 Gy 2.1 vs 1.4, P = 0.02). 

“Follow-up of patients who received abdominal irradiation should include diabetes,” the authors advised.