Pediatric brain tumors: An overview

that brain tumors are diagnosed in approx imately 1,200 to 1,500 children each year.' The yearly accrual of the various histologic subtypes of brain tumors is, therefore, cor respondingly small. In addition, because only about 50 percent of children with brain tumors are referred to university or cancer treatment centers,2 therapeutic trials, by default rather than design, have been re stricted to small numbers of patients. Another complication is the lack of a universally accepted histologic classifica tion or grading system for brain tumors. The World Health Organization (WHO) classification has been inadequate for a substantial proportion of brain tumors in children. The lack of uniformity in clas sification results in the inability to accu rately evaluate prognosis based on histology from one center to another. Similarly, re ported responses to treatment are often dif ficult to assess. In addition, there are neither well established clinical and surgical staging criteria, nor universally accepted defini tions of response and relapse. As with other tumorsof childhood,stagingsystemsfor braintumorsmay establish guidelines that permit prognosis based on extent of disease at diagnosis and postoperatively. Medul loblastoma has been the only CNS tumor for which an effort has been made to cor relate surgical staging with prognosis. Subsequent evaluations have indicated that staging in this tumor may have prognostic significance. Introduction