Age curves of central nervous system tumor incidence in adults: variation of shape by histologic type

Data from nine population-based cancer registries from the National Cancer Institute's Surveillance, Epidemiology, and End Results program of the United States were used to study the incidence of individual histologic types of malignant central nervous system tumors by age and sex among adults. On a log-log scale, incidence increased linearly between the ages 35 and 64, with a slope that was not different between males and females or among registries but that varied by histologic type. The estimated slopes were 0.4 for ependymomas, 1.0 for oligodendrogliomas, 1.7 for astrocytomas, 2.8 for meningiomas, and 3.9 for glioblastomas. The rate at which incidence increased with age was significantly higher for glioblastomas than for other glial tumors. This finding suggests a different mechanism of carcinogenesis for glioblastomas than for other glial tumors.