Childhood cancer survivors - especially those whose treatment included brain irradiation or chemotherapy with glucocorticoids - are 14 percent more likely to be obese than their healthy peers. The St. Jude Children’s Research Hospital study appears today in the journal Cancer.
Of the 1,996 childhood cancer survivors in this study, 36.2 percent had a body mass index (BMI) of 30 kilograms per meters squared or more, which qualifies as obese. That was 14 percent greater than the expected prevalence based on federal health survey data of a comparison group of U.S. residents.
Among the strongest predictor of obesity in survivors was childhood obesity, which is also a strong predictor of adult obesity in the general public. Survivors who were obese when their pediatric cancer was discovered were almost five times more likely than other survivors to be obese when their BMI was calculated for this study.
Other obesity risk factors were age and childhood cancer treatment. Survivors who were ages 30 and older when their BMI was calculated were more likely than younger survivors to be obese. Also, 47 percent of survivors who received brain irradiation as part of their treatment were obese, compared to 29.4 percent of survivors who received other therapies. The risk increased for survivors whose cancer was diagnosed when they were younger than age 4 and whose treatment included glucocorticoids.
In comparison, survivors treated with chest, abdominal or pelvic irradiation were about half as likely as other survivors to be obese.
“The high prevalence of obesity in cancer survivors is of great concern and underscores the need to develop more effective counseling and weight-loss interventions for this growing population,” said first author Carmen Wilson, Ph.D., a research associate in the St. Jude Department of Epidemiology and Cancer Control.
- Being overweight or obese is a risk factor for several types of cancer. Although a higher weight may not necessarily cause cancer, maintaining a healthy weight is thought to be associated with a lower risk of many chronic diseases.
- Many resources are available to help you maintain a healthy weight, including doctors and dietitians.
- Talk with your doctor about developing an appropriate weight control plan for you.
More than two-thirds of American adults are overweight or obese (substantially or extremely overweight). When a person is overweight or obese, it means that they have too much body fat in relation to lean body tissue, such as muscle. Many factors cause people to become overweight or obese, including genetic, hormonal, environmental, emotional, and cultural factors. People who are overweight or obese have a higher risk of many serious health conditions, including type II diabetes, high blood pressure, and heart disease. Being overweight or obese is also associated with an increased risk of cancer.
Corresponding author Kirsten Ness, Ph.D., a member of St. Jude Epidemiology and Cancer Control, added: “Childhood cancer survivors are known to be prone to developing chronic disease. Obesity just adds to that risk.”
In the general public, obesity is associated with an increased risk of premature death as well as cancer, heart disease and other chronic health problems. St. Jude researchers are working on more effective weight management strategies for childhood cancer survivors, some possibly starting shortly after the cancer diagnosis.
The current study is one of the first to explore how genetics may impact obesity in childhood cancer survivors and the first to scan the entire genome for small variations in DNA that may influence the risk of treatment-related obesity.
Researchers identified four regions of genetic variation associated with a greater likelihood of obesity following brain irradiation, a therapy used to treat brain tumors in some patients, but no longer used to treat St. Jude patients with acute lymphoblastic leukemia (ALL). The genetic regions identified were in and around genes that have been implicated in nervous system development. The genes are FAM155A, SOX11, CDH18 and GLRA3.
“The results must be verified, but the findings suggest that variations in genes responsible for neural growth, repair and connectivity may modify the risk of obesity in childhood cancer survivors treated with cranial irradiation,” Wilson said. “Understanding the genetic basis of why certain survivors are more vulnerable to treatment-induced health problems may help us identify high-risk patients and develop strategies to reduce or better manage their risk.”
Information about diet, exercise and other lifestyle factors that influence obesity was not available for study participants.
Obesity is quickly overtaking tobacco as the leading preventable cause of cancer, and although data are still emerging, research suggests that the risk of developing and dying from many common cancers is increased in obese individuals. Obesity is also linked to poorer cancer outcomes, including increased risk of recurrence and of both cancer-specific and overall mortality.
Oncologists play a critical role in patient education, as well as in education of caregivers and families, regarding the importance of weight management. Oncologists are also often the main source of referrals to appropriate sources where patients and their families can receive sound guidance. ASCO is committed to informing oncology providers regarding the existing data linking obesity, inactivity and poor diet to poor outcomes in patients with cancer and to provide educational materials for patients regarding the role of weight management and healthy lifestyle behaviors in cancer.
The average survivor in this study was 32 years old and almost 25 years beyond a cancer diagnosis, making this among the most comprehensive efforts yet to understand obesity in childhood cancer survivors. The research was part of the St. Jude Lifetime Cohort Study (St. Jude LIFE), which brings cancer survivors treated at St. Jude back to the hospital for several days of health screenings and other assessments. St. Jude LIFE is the centerpiece of the hospital’s ongoing efforts to improve medical care and the quality of life for current and future childhood cancer survivors.
Treatment-related risk factors help to explain the high rate of obesity among childhood ALL survivors. In this study, 43 percent of the ALL survivors were obese, which is higher than the 19 to 32 percent reported in previous research.
The study is one of the largest yet involving survivors of pediatric solid tumors. “We found that the frequency of obesity in solid tumors survivors was higher than had been previously reported,” Wilson said. With the exception of female survivors of kidney cancer, more than 25 percent of solid tumor survivors in this study were obese.
The other study authors are Wei Liu, Jun J. Yang, Guolian Kang, Rohit Ojha, Geoffrey Neale, Deo Kumar Srivastava, James Gurney, Melissa Hudson and Leslie Robison, all of St. Jude.
The research is funded in part by a grant (CA021765) from the National Cancer Institute at the National Institutes of Health and ALSAC.
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