Cancer in children is a heterogeneous group of diseases with regard to histology, localization, proliferating capacity, type of spread, and response to treatment. At least 50 different types of tumors and leukemias are known. Cancer in children is not frequent as compared with cancer in adults. However, it has remained first among the causes of natural death in children and adolescents, being surpassed only by deaths due to poisoning and accidents. Its incidence is 12-14 per 100,000 children per year. Thus, in populations of Western Europe and the United States of America and Canada, 1,200 newly diagnosed childhood cancers will occur in a population of 40 million people, if we presume that 25% of the population is younger than 16 years.
There have been great efforts to overcome these lifethreatening diseases during the past 30 years. These efforts were multidisciplinarily based, and they have led to great successes. Basic and clinical reasearch have contributed to these, as have improvements in diagnostic and therapeutic techniques. Thus, the mortality of childhood cancer has probably been reduced by 50% during the past 30 years.
About 15% of children with cancer are cases for the urologist. This is true for children with testicular cancer, Wilms' tumors, abdominal neuroblastoma, and urogenital rhabdomyosarcoma as well as for the eventual child with testicular leukemia or lymphoma. An important issue has emerged with the growing number of malignant primitive neuroectodermal tumors, which occasionally arise in the retroperitoneum or pelvis and may be a urological problem.
Cure is possible in about 50% of cases of urogenital malignancies in children, but treatment efforts have to be intensive and are mostly based on radical surgery and multidrug chemotherapy plus eventual radiotherapy. These treatment modes may be followed by side effects. Therefore, close and thorough posttreatment follow-up is mandatory. It may reveal late sequelae, which may pose new treatment problems for the urologist.