Cranial Radiotherapy for Childhood ALL Linked to Adult Obesity

NIAGARA-ON-THE-LAKE, Ontario, Canada—Treatment for acute lymphoblastic leukemia (ALL) as a child may increase the risk for obesity in adulthood, and a new study suggests that cranial irradiation may be a factor. The results (abstract 13) were presented at the 7th International Conference for Long-Term Complications of Treatment of Children and Adolescents for Cancer, hosted by Roswell Park Cancer Institute.

"Obesity is a serious health condition," said Kevin Oeffinger, MD, Department of Family Practice and Community Medicine, The University of Texas Southwestern Medical Center at Dallas. "It can lead to other serious health conditions such as diabetes and hypertension. We should know if the treatment for ALL predisposes this population to additional health risks and help with appropriate interventions."

This study evaluated 1,765 adult survivors of ALL who participated in the Childhood Cancer Survivor Study (CCSS). The CCSS is a resource designed to investigate the long-term effects of cancer treatment among 5-year survivors of childhood and adolescent cancer. The ALL survivors were compared with 2,565 cancer-free siblings; 47,555 participants from the National Health Interview Study (NHIS) were also studied.

The mean age was 24.1 years for the leukemia survivors and 29 years for the siblings. The survivors’ mean age at diagnosis was 7.5 years (range, 0.1 to 20.8), and the study was conducted a mean of 17.1 years after their diagnosis (range, 7.4 to 27.5). The survivor group was 49% female and the siblings were 53% female.

Participants were asked to provide their current height and weight. Using these self-reported figures, a body mass index (BMI) was calculated to determine the obesity rate. The national standard was used in which a BMI of 30 or greater represents obesity and 25 to 29.9 represents overweight.

After adjusting for sex and age, there were no significant differences in weight between the sibling group and the NHIS group. However, there were differences for the survivor population, compared with their siblings, depending on the type of treatment they received.

The age- and race-adjusted odds ratio for obesity for ALL survivors treated with chemotherapy and cranial radiation of 20 Gy or more, compared with siblings, was 2.59 for females (P < .001) and 1.86 for males (P < .01). In particular, for females diagnosed between 0 and 4 years of age, the risk, compared with siblings, was 3.81 (P < .001).

No increase in obesity rates was found in ALL survivors who were treated with chemotherapy only or with chemotherapy plus cranial radiation doses of between 10 and 19.9 Gy.

Girls Treated Under Age 4

"We found that in the survivor group, age played a role for survivors who were treated with 20 Gy or more of cranial radiation and chemotherapy. The adjusted risk for obesity for girls treated under the age of 4 is significant and it is a striking observation," Dr. Oeffinger said.

He stressed the need to investigate possible causes for this problem. "Most likely, these changes are, in part, related to radiation-induced injury to the hypothalamic-pituitary axis, resulting in leptin insensitivity and/or alterations in growth hormone secretion," he said.

Regardless of the exact cause, Dr. Oeffinger said, "as health care professionals, we need to recognize this risk and develop strategies for weight control and screen for obesity-related diseases in this survivor population."