title: A population-based study of the incidence and survival rates in patients with pilocytic astrocytoma.
abstract: OBJECTIVE
  The incidence of pilocytic astrocytomas and the rate of patient survival were analyzed in a population-based study in the canton of Zürich, Switzerland.
  
  
  METHODS
  Between 1980 and 1994, 987 astrocytic and oligodendroglial tumors were diagnosed, of which 55 (5.5%) were pilocytic astrocytomas. The incidence rate, adjusted to the World Standard Population, was 4.8 per 1 million per year. The mean age at clinical diagnosis was 19.6 +/- 12.7 years, and the male/female ratio was 1.12. The most frequent tumor sites were the cerebellum (40%), followed by supratentorial locations (35%), the optic pathway and hypothalamus (11%), and the brainstem (9%). The mean follow-up period was 12 years. Observed survival rates were 100% at 5 years and 95.8% at 10 years after diagnosis (relative survival rate at 10 years: 96.8%). Seven patients (13%) received postoperative radiotherapy, but this did not significantly affect survival. In all patients the tumors were histologically classified as WHO Grade I, except in two patients who had anaplastic pilocytic astrocytoma (Grade III), one of whom died after 7 years, whereas the other was still alive after 10 years.
  
  
  CONCLUSIONS
  This population-based study shows that, because of the benign biological behavior of pilocytic astrocytomas and advances in microneurosurgery, the survival rates for patients with these tumors are excellent, regardless of postoperative radiotherapy.
authors.affiliation: International Agency for Research on Cancer, Lyon, France.
authors.forename: Christoph
authors.initials: C
authors.lastname: Burkhard
authors.forename: Pier-Luigi
authors.initials: PL
authors.lastname: Di Patre
authors.forename: Danielle
authors.initials: D
authors.lastname: Schüler
authors.forename: Georges
authors.initials: G
authors.lastname: Schüler
authors.forename: M Gazi
authors.initials: MG
authors.lastname: Yaşargil
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yonekawa
authors.forename: Urs M
authors.initials: UM
authors.lastname: Lütolf
authors.forename: Paul
authors.initials: P
authors.lastname: Kleihues
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ohgaki
mesh_terms: D000328:Adult; D001254:Astrocytoma / Q000453:epidemiology* / Q000401:mortality / Q000601:surgery; D002391:Catchment Area, Health; D016543:Central Nervous System Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000601:surgery; D002531:Cerebellum / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007031:Hypothalamus / Q000601:surgery; D015994:Incidence; D008297:Male; D009367:Neoplasm Staging; D011159:Population Surveillance; D012042:Registries; D012189:Retrospective Studies; D015996:Survival Rate; D013557:Switzerland / Q000453:epidemiology