Several studies have reported increased incidence trends of malignant gliomas in the late 1900’s with a plateau in the 2000’s, but also some recent increases have been reported. The purpose of our study was to analyze incidence trends of malignant gliomas in Finland between 1990 and 2006 by morphology and site.

Data on 4,730 malignant glioma patients were obtained from the nationwide, population-based Finnish Cancer Registry. Age-standardized incidence rates and average annual percent changes in the incidence rates were calculated by histological subtype and tumor location.

The incidence rate of gliomas was 9.3 per 100,000 for men and 6.5 for women. The incidence of all gliomas combined was stable (annual percent change +0.1%; 95% CI: −0.5, +0.7), with no departure from linearity. In an analysis by age group, increasing incidence was found only for ages 80 years and older. Incidence rates were increasing in anaplastic oligodendroglioma, oligoastrocytoma and unspecified malignant glioma, with a minor increase also for glioblastoma. Correspondingly, decreasing rates were observed for astrocytoma and unspecified brain tumors. As for tumor location, incidence was increasing for frontal lobe and brainstem tumors, as well as those with an unspecified location, but decreasing for the parietal lobes, cerebrum and ventricles.

No increasing incidence trend was observed for all malignant gliomas combined. An increasing incidence trend of malignant gliomas was found in the oldest age group.