Changing incidence and improved survival of gliomas

Tumours of the central nervous system (CNS) represent a relatively rare but serious health burden. This study provides insight into the incidence and survival patterns of gliomas in the Netherlands diagnosed in adult patients during the time period 1989-2010, with a focus on glioblastoma and low-grade gliomas.

Data on 21,085 gliomas (excluding grade I tumours) were obtained from the Netherlands Cancer Registry, including tumours of the CNS without pathological confirmation. We calculated the age-standardised incidence rates and the estimated annual percentage change (EAPC) for all glioma subtypes. Crude and relative survival rates were estimated using information on the vital status obtained from the Dutch Municipal Personal Records Database.

Incidence of gliomas in adults increased over time, from 4.9 per 100,000 in 1989 to 5.9 in 2010 (EAPC 0.7%, p<0.001). Two thirds were astrocytoma, 10% oligodendroglioma/oligoastrocytoma, 3% ependymoma and 21% were unspecified. Within the group of astrocytic tumours, the proportion of glioblastoma rose, while the proportion of anaplastic and unspecified astrocytoma decreased. Unspecified neoplasms also decreased, but this was significant only after 2005. Over the course of the study period, glioblastoma patients more often received multimodality treatment with chemotherapy concomitant and adjuvant to radiotherapy. The crude two-year survival rate of glioblastoma patients improved significantly, from 5% in the time period 1989-1994 to 15% in 2006-2010, with median survival increasing from 5.5 to 9 months. The incidence of low-grade gliomas did not change over time. Survival rates for low-grade oligodendroglial and mixed tumours show a modest improvement.

The incidence rate for the total group of gliomas slightly increased, with a decrease of anaplastic and unspecified tumours and an increase of glioblastoma. Following the introduction of combined chemoradiation, two-year survival rates for glioblastoma significantly improved. Survival improved for low-grade gliomas except for low-grade astrocytic tumours.