Thyroid cancer in children and young adults in the North of England. Is increasing incidence related to the Chernobyl accident?

Population-based data on thyroid carcinomas was obtained from the Northern Region Young Person's Malignant Disease Registry to analyse the incidence o f thyroid cancers in young people (< 25 years) in the North of England for the period 1968 and 1997 and to assess if changes in incidence were consist ent with the spatial and temporal distribution of the fallout from the Cher nobyl nuclear accident. We compared incidence rates for differentiated (pap illary or follicular) thyroid carcinomas 1968-1986 with those for 1987-1997 . There were 75 cases of thyroid carcinoma diagnosed over the study period, of which 63 were differentiated carcinoma and 12 were medullary carcinoma. There were 26 young adults (15-24 years) diagnosed with differentiated thy roid carcinoma in the 19-year period 1968-1986 and 30 in the subsequent 11 years 1987-1997, Age standardised rate (ASR) 3.0 versus 6.5, respectively ( rate ratio 2.2, 95% confidence interval(CI): 1.3-3.6). There were three chi ldren (aged < 15 years) diagnosed with differentiated carcinoma in the: per iod 1968-1986 and four in the period 1987-1997, ASR 0.2 versus 0.6 (rate ra tio 2.7, 95% CI: 0.6-12.1). Regression models showed a significant increase in the incidence of thyroid cancer after the Chernobyl accident (P = 0.002 ). In Cumbria. the area receiving the heaviest fallout in the UK. the incre ase in incidence was much greater (rate ratio 12.19, 95% CI 1.5-101.2). The se temporal and spatial changes in incidence are consistent with a causal a ssociation with the Chernobyl accident although a greater effect in the you nger rather than the older age group would have been anticipated. However, factors including improvements in ascertainment and earlier detection of ru mours may also have contributed to the increasing incidence. Further collab orative international studies are needed to investigate changes in the inci dence of thyroid cancer in children and young adults. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.