Are reported increases in incidence of primary CNS tumours real? An analysis of longitudinal trends in England, 1979-2003.

Reported increases in the incidence of CNS tumours in the developed world in the 1970s to 1990s have been a cause for concern and debate. It still remains to be adequately answered whether these increases are true or an artefact of changes in diagnostic and registration practices. Using high-quality national cancer registration data, we have analysed incidence trends for each major histological subgroup of CNS tumour (2000 World Health Organisation (WHO) classification) registered in those aged 0-84 years for the whole of England during the period 1979 through 2003. 134,509 primary CNS tumours of malignant, benign and uncertain behaviour located in the brain, meninges, spinal cord, cranial nerves, other parts of the central nervous system and in the pituitary and pineal glands were registered. In summary, we present the single largest nationwide study on the longitudinal incidence trends of CNS tumours. The increase in incidence observed in the 1970s and 1980s was mainly in the young and the elderly and has now plateaued and may even be decreasing. There is however variation in trends by histology. The incidence of some histological sub-groups has continued to increase until the most recent period of analysis. Much of the initial increase can be attributed to the emergence of much more widely available neuroimaging, while the most recent incidence changes for specific sub-groups of CNS tumours appear to be due to greater diagnostic specificity leading to a shift in registered categories. However, the trends for high-grade astrocytomas and other gliomas need further observation and investigation.