Obesity and Risk for Second Malignant Neoplasms in Childhood Cancer Survivors: A Case–Control Study Utilizing the California Cancer Registry

BACKGROUND: Obesity is a known modifiable risk factor associated with adverse outcomes in children with cancer. We sought to determine whether obesity during childhood cancer treatment increases risk for second malignant neoplasms (SMN). METHODS: In this case-control study, cases (with SMN) and controls (with a single-primary cancer) were selected from the California Cancer Registry who had primary cancer diagnosed <21 years treated at Children's Hospital Los Angeles between 1988 and 2014. Controls were matched 3:1 to cases at the registry level by clinical factors. Medical records were abstracted for cancer treatment exposures, cancer predisposition syndrome, body mass index (BMI), BMI Z-score, and BMI category at diagnosis and end of therapy (EOT). RESULTS: A total of 59 cases and 130 controls were included. Median age at primary cancer diagnosis was 6 years, 64.5% were male, median time from primary cancer to SMN was 7.5 years, and 31.7% were obese or overweight. In matched multivariable analyses, there were elevated but nonsignificant associations between SMN and higher BMI Z-score at diagnosis [OR 1.27 (0.99-1.63)] and higher BMI categories at diagnosis [adjusted OR (aOR) overweight, 1.25 (0.55-2.52); aOR obese, 2.51 (1.00-6.29)]. There was a significantly increased risk for SMN among patients who were obese at both diagnosis and EOT [aOR, 4.44 (1.37-14.34)]. CONCLUSIONS: This study suggests that obesity during childhood cancer treatment may be associated with increased risk for SMNs, particularly among those obese throughout therapy. IMPACT: Additional studies to confirm these findings and to develop interventions have the potential to impact SMN development in children with cancer.