Sexually dimorphic and radiation dose dependent effect of cranial irradiation on body mass index

Objectives-To investigate the relation between cranial irradiation received during treatment for childhood leukaemia and obesity at final height. Design-Retrospective cross sectional study. Setting-Paediatric oncology centres at Great Ormond Street Hospital for Chi ldren and the Royal Marsden Hospital. Subjects-Survivors of childhood leukaemia who received cranial irradiation, were in continuous first remission, and had reached final height. An unirr adiated group of patients fi om the United Kingdom acute lymphoblastic leuk aemia XI trial was also included; these patients were in continuous first r emission and had been followed for at least four years from diagnosis. Main outcome measures-Body mass index standard deviation score (BMI z score ) at final height for irradiated patients and at most recent follow up for unirradiated patients. Regression analysis was used to examine the effect o n BMI z score of sex, age at diagnosis, and the dose of radiation received. Results-For cranially irradiated patients, an increase in the BMI z score a t final height was associated with female sex and lower radiation dose, but not with age at diagnosis. Severe obesity, defined as a BMI z score of > 3 at final height, was only present in girls who received 18-20 Gy irradiati on and had a prevalence of 8%. Both male and female unirradiated patients h ad raised BMI z scores at latest follow up and there was no association wit h age at diagnosis. Conclusions-These data are further evidence for a sexually dimorphic and do se dependent effect. of radiation on the human brain.