小児がん

～1．小児がんの疫学と発生要因～

抄録

  The prevalence of childhood cancer has been estimated to be 1 to 1.5 per 10,000 persons. Although childhood cancer is less common than adult cancer, about 3000 new patients are registered per year. Childhood cancer is the second leading cause of death in children, after accidents. Owing to progress in diagnostic and therapeutic techniques, more than 70% to 80% of patients are now cured. Because cancer develops in 1 per 500 to 600 children aged 0 to 14 years, it is estimated that about 1 per 300 of the entire population has had childhood cancer. Childhood cancer is characterized by a high prevalence of blastomas and sarcomas, derived from fetal tissue and precursor cells. Tumors can arise in various sites, and tumor type is related to age and sex. Generally, childhood cancers are sensitive to antitumor agents and radiotherapy; however, response rates, remission rates, and long-term survival rates differ depending on tumor type, molecular biologic and cellular genetic characteristics, and tumor extension. Treatment is therefore decided according to expected outcomes, predicted on the basis of risk factors.
  The development of childhood cancer is mainly related to genetic predisposition, the fetal environment from conception to birth, and genetic abnormalities occurring during postnatal growth and development. Unlike adult cancer, the effects of lifestyle and environmental factors are minimal. Studies of genetic diseases associated with high risks of cancers such as retinoblastoma and chromosomal and genetic analyses of cancer cells in diseases such as neuroblastoma and leukemia have led to the identification of many oncogenes and tumor suppressor genes, contributing to a better understanding of the mechanisms underlying the development and progression of cancer, the identification of risk factors, and the development of molecular targeted therapy.
  Progress in epidemiology, molecular biology, and cellular genetics is changing childhood cancer from an incurable to a curable disease. How to improve patients' quality of life after treatment (i.e., a decreased rate of late complications) is becoming an important part of the treatment strategy.