White and brown adipocytes differ in their expression of hormones, cytokines, and inflammatory factors, and they modulate different biological functions. While white adipose tissue (WAT) serves as the primary site of energy storage, brown adipose tissue (BAT) instead metabolizes fat to produce heat and regulate body temperature. BAT is likely present in all humans, but the low prevalence of BAT depiction in adults and elderly subjects has hindered longitudinal assessments of the relation between BAT activity and WAT. Under typical imaging conditions, BAT is detected more frequently in children and teenagers than in adults with malignancy. Since most children with cancer have significantly shorter treatment courses and greater survival rates compared to adult patients, the investigators have the ability to examine the relation of repeated measures of body composition and BAT by selecting pediatric patients. In this study, the investigators will longitudinally examine whether BAT activity is related to changes in weight and the amounts of SAT, VAT, and abdominal muscle in children successfully treated for pediatric cancer.

Inclusion Criteria:

• Patients had PET/CT scans with evidence of malignant disease
• Patients had no metabolically active BAT at diagnosis on their PET/CT scan
• Patients were disease free within 1 year of diagnosis

Exclusion Criteria:

• Patients had PET/CT scans with no evidence of malignant disease
• Patients with metabolically active BAT at diagnosis on their PET/CT scan
• Patients were not disease free within 1 year of diagnosis

Pediatric patients with a history of malignancy such that they are required to undergo PET/CT exams.