Infants with Cancer: A Unique Population

Cancer occurring in infants often has a clinical and biological behavior that is different from cancers occurring in older children. The histological distribution of cancers in infants is different from that in older children. The five most common types of cancer occurring in infants in Taiwan are leukemia, neuroblastoma, germ cell tumors, central nervous system neoplasms, and retinoblastomas. Cancer in infants represents a unique situation in which to study cancer etiology. A significant number of infants with cancer have a genetic susceptibility to the disease; however, some emerging studies suggest a potential role for environmental, dietary, and drug exposures in the etiology of infant cancers. Further definitive trials will be necessary to establish clear associations, however. Because of their very young age and the immaturity of many of their physiological systems, the approach to treatment in young infants differs from that in older children. The infant's response to treatment also differs from older children, indicating the unique biological properties of cancer in infants that may explain different clinical outcomes in this unique population. Infant acute lymphoblastic leukemia has a much inferior outcome compared with the outcome in older children. In contrast, neuroblastoma in infants has a superior outcome to that seen in older children. The care of infants with cancer is extremely challenging as a result of their increased vulnerability to the acute complications associated with intensive, multimodal treatment and to the long-term sequelae of chemotherapy and radiotherapy on the rapidly growing and developing infant. The chemotherapy-related toxicity seen in very young infants of less than 3 months of age may be due to a lower total body water content, lower P450 enzyme activity, lower serum protein binding, and immature renal function. The high susceptibility of immature tissues to radiotherapy-induced damage has led to the delivery of radiotherapy being limited in this age group. Protocols specific to the characteristics of this population are currently yielding promising results.