A 22-Year Retrospective Epidemiological Review Of Thyroid Cancer Trends In Northern Ireland: 1993-2014

Thyroid cancer incidence has increased globally since the 1970s.1 It is important to analyse thistrend in different countries over time for trend comparison. We aimed to describe Northern Ireland’s(NI’s) trends between 1993-2014 analysing by sex, age, stage and morphology.A retrospective, descriptive epidemiological review of NI’s trends, 1993-2014, was conducted withanonymised data obtained from the Northern Ireland Cancer Registry. C73 is the thyroid cancerICD-10 code. We used STATA to calculate incidence statistics and Joinpoint Regression Analysisto analyse trend significance. Registry ethical approval was previously granted.There were 1,212 cases in total (27.06% male, 72.94% female, F:M=2.7:1). Incidence increasedsignificantly in females (1999-2014, annual percentage change (APC) +4.64%, p<0.05, 95%confidence interval (CI) +2.4, +6.9). Frequency increased predominantly in ages 40-64(1995-2014, APC +4.66%, p<0.05, CI +2.5, +6.9). 55.63% of the 320 cases with staging data(2010-2014) were stage I. Papillary carcinoma frequency increased dramatically (2004-2014, APC+11.01%, p<0.05, CI +5.8, +16.4).This study shows that incidence has increased in NI in the last 2 decades in females and middleagedpatients. This is mainly due to papillary carcinomas, potentially mostly stage I. This data maysupport the hypothesis that over-diagnosis has resulted in apparent increasing trends.2,31. Kilfoy BA, Zheng T, Holford TR, Han X, Ward MH, Sjodin A, et al. International patterns andtrends in thyroid cancer incidence, 1973–2002. Cancer Causes & Control. 2009;20(5):525-31.2. Davies L, Welch HG. Increasing incidence of thyroid cancer in the United States, 1973-2002.JAMA. 2006;295(18):2164-7.3. Kent WD, Hall SF, Isotalo PA, Houlden RL, George RL, Groome PA. Increased incidence ofdifferentiated thyroid carcinoma and detection of subclinical disease. CMAJ. 2007;177(11):1357-61.