Incidence and time trends of childhood cancer in Denmark, 1943-2014.

Surveillance of childhood cancer incidence is informative for etiologic research and health policy. However, high-quality data covering several decades of virtually complete cancer diagnosis in children is sparse. Incident cases of childhood cancer (0-19 years at diagnosis), classified according to Birch and Marsden's International Classification of Childhood Cancer, first edition (ICCC-1), were identified in the Danish Cancer Registry and used to calculate age-standardized incidence rates (ASRs) and estimated annual percentage change (EAPC) separately for 1943-1977 (early period) and 1977-2014 (recent period). During 1943-2014, 15,184 childhood cancer cases were reported. The ASR for any cancer was 13.0 per 100 000 person-years in the early period (EAPC 0.55%; 95% CI 0.30-0.80) and 17.7 per 100 000 person-years in the recent period (EAPC 1.16%; 95% CI 0.96-1.36). In both periods, the increasing trend was seen in both boys (EAPC 0.69%; 95% CI 0.43-0.96/EAPC 0.96%; 95% CI 0.75-1.17) and girls (EAPC 0.37%; 95% CI -0.01-0.75/EAPC 1.41%; 95% CI 1.11-1.72) and in children aged 0-14 years (EAPC 0.53%; 95% CI 0.26-0.80/EAPC 0.86%; 95% CI 0.64-1.08) and 15-19 years (EAPC 0.60%; 95% CI 0.19-1.02/EAPC 1.97%; 95% CI 1.67-2.28). Increasing trends were observed for all main diagnostic groups. The incidence of childhood cancer in Denmark has increased since the 1940s, especially since 1977 and in older children. In recent years the increase has been most pronounced among girls.