Cancer among teenagers in Denmark, 1943-1987.

A population-based study was carried out on 3,988 tumours in teenagers (aged 10-19 years) diagnosed during the period 1943-87 in Denmark and abstracted from the files of the National Cancer Registry. In that Registry, codes for tumours were based solely on topography until the end of 1977. In order to obtain a uniform data set, coded by the system of the International Classification of Diseases for Oncology (ICD-O) now used at the Cancer Registry, all cases of teenage cancer diagnosed prior to 1978 were re-evaluated, and an ICD-O code was applied. Tumours were further aggregated into diagnostic groups using an internationally agreed scheme. The average incidence rates for all histological types combined were 136 per million for boys and 108 per million for girls, which are close to those reported in Connecticut, USA. Central nervous system tumours, leukaemia and malignant lymphomas accounted for 60% of all cancers among teenagers. An overall excess of cancers among boys was mainly due to more frequent occurrence of leukaemias, malignant lymphomas, sarcomas and germ-cell tumours. Increasing trends with time were seen for malignant lymphomas in both boys and girls and for subtypes of non-seminoma germ-cell tumour among boys aged 15-19. For other diagnostic groups, including the main group of leukaemias, the rates have remained largely unchanged, suggesting that environmental factors associated with modern society play a minor role in the aetiology of cancer among teenagers.