Trends in the incidence of primary intracranial tumors in Kumamoto, Japan

Abstract

Background. The introduction of modern neuro-imaging techniques, as well as various environmental factors, have been changing the incidence and the proportions of the types of clinically diagnosed intracranial tumors. The aim of this study was to determine recent trends in the occurrence of primary intracranial tumors in the residents of Kumamoto Prefecture, Japan.

Methods. We surveyed 2129 patients who were diagnosed with primary intracranial tumors between 1989 and 1998, with histological diagnosis being obtained in 71% of the patients.

Results. Of the 2129 patients, 710 (33.3%) had meningiomas, 390 (18.3%) had pituitary adenomas, 315 (14.8%) had malignant gliomas, and 208 (9.8%) had schwannomas. The overall age-adjusted incidence rates were 10.97/100 000/year (males, 9.70; females, 11.86). One hundred and nine patients (5.1%) were younger than 15 years, and 480 patients (22.5%) were older than 70 years. The most common tumors in children were astrocytomas (37.6%), followed by germ-cell tumors (16.5%) and craniopharyngiomas (11.9%), medulloblastomas (11.0%), and ependymomas (4.6%). Meanwhile, the most common tumors in elderly residents were meningioma (51.7%), followed by malignant glioma (13.7%), pituitary adenoma (11.4%), schwannoma (7.7%), malignant lymphoma (4.6%), and astrocytoma (2.7%). The proportion of asymptomatic tumors increased, from 24.6% in 1989–1994 to 33.0% in 1995–1998; 169 (62.8%) were meningiomas, followed by pituitary adenomas (14.1%).

Conclusion. The detection rate of asymptomatic intracranial tumors, particularly that of meningiomas, and the incidence of brain lymphoma are on the increase. Differences in the incidence of gliomas, pituitary adenomas, medulloblastomas, and germ-cell tumors between the Japanese population and populations in Western countries may be attributable to ethnic differences.