Childhood cancer patients may be at risk of obesity in later life due to the side effects of certain treatments. A new study published in the journal Cancer suggests that weight loss interventions and counseling may be needed for these survivors of childhood cancer.

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Studies have found an association between obesity in adulthood and exposure to cranial radiation during childhood.

Studies have previously found an association between obesity and exposure to cranial radiation as a cancer treatment during childhood. The highest risk in these studies was observed among female survivors and those who had been diagnosed at a younger age.

In these cases, weight gain was found to accelerate with age. Scientists hypothesized that the weight gain may be associated with damage caused by radiation to a brain area called the hypothalamic-pituitary axis.

This kind of radiation damage is “a complex, integrated cellular and intracellular response” within tissue that involves inflammation, the production of reactive oxygen species and cell death. Researchers have also suggested that some genetic factors may influence how susceptible patients receiving radiation therapy are to these toxicities.

The researchers behind the new study, from St. Jude Children’s Research Hospital in Memphis, TN, wanted to estimate the prevalence of obesity among survivors of childhood cancer and also identify what risks in treatment or genetic factors that may contribute to obesity in these patients.

The team analyzed data from 1,996 childhood cancer survivors who had been diagnosed with cancer at least 10 years ago and treated at St. Jude.

The study reports that 47% of the patients who had received cranial radiation were now obese, compared with 29.4% of participants who were not treated with cranial radiation. Survivors treated with chest, abdominal or pelvic radiation were found to be half as likely to be obese as survivors who did have these kinds of radiation.

Patients treated with cranial radiation who also received glucocorticoids had an even stronger association with obesity, as did patients who were younger at the time of their diagnosis.

The researchers also identified a genetic risk factor – survivors with gene variants involved in the repair, growth and connectivity of neurons were more likely to be obese if they had been treated with cranial radiation.

Study leader Dr. Carmen Wilson says that “the ability to identify patients at increased risk may guide selection of therapeutic protocols that will maximize treatment outcomes while simultaneously minimizing the risk of long-term complications among children diagnosed with cancer.”

Dr. Wilson also hopes that the findings will provide the basis of future studies into characterizing molecular pathways involved in the association between obesity and childhood cancer treatment.

The researchers say that one strength of their study was the use of a large cohort of adult survivors, over half of which were more than 25 years from diagnosis of their childhood cancer. However, the researchers did not have access to data on obesity status following completion of therapy or data on lifestyle factors, which may have influenced obesity risk.