Analysis of the Thyroid Carcinoma Incidence in Tianjin Over a Recent Twenty-Year Period ======================================================================================= * Biyun Qian * Kexin Chen * Min He * shufen Dong * Haixin Li * Fengju Song ## Abstract **OBJECTIVE** To analyze the incidence rate and trend of thyroid cancer in Tianjin over a recent 20-year period. **METHODS** A method of descriptive epidemiology was used to study the occurrence of thyroid cancer. **RESULTS** During 1981 ∼2001, the average incidence rate of thyroid cancer was 1.770 per 100,000 with a male to female incidence ratio of 1:2.74, the occurrence being higher in females than in males. Thyroid cancer incidence increased gradually with time over the 20 years in both males and females, especially the incidence peaked in females of 35∼50 **CONCLUSION** The rapid increase in the incidence rate of thyroid canInstitute and cer, especially in females, suggests that further research on the risk factors and preventive efforts related to high -risk women should be con ducted. KEYWORDS: * thyroid cancer * epidemiology * incidence rate * time trend While being relatively rare overall, thyroid cancer is the most prevalent endocrine malignancy which mostly affects young women. However because the incidence and mortality are relatively lower than other cancers, to the best of our knowledge there has been no population-based study in China. This study is a statistical analysis of the incidence and trends of thyroid cancer in Tianjin from 1981 to 2001, and thus provides insight for future research on the cause of the trends and etiology of thyroid cancer. ## MATERIALS AND METHODS ### Data All of the cases were from the Tianjin Cancer Registry that was established in 1978. This registry is one of the members of the International Agency for Research on Cancer (IARC) of the World Health Organization. Since 1981 the cancer incidence data from Tianjin has been included in the IARC official publication: "Cancer Incidence in Five Continents". In our study, we included all primary thyroid cancer patients (ICD-9 codes 192) from 1981 to 2001 in the Tianjin urban population. Numbers in each age-sex specific population for the 6 urban districts were obtained from the Tianjin Public Security Bureau. ### Descriptive analyses The statistical analysis was carried out using SAS 8.1 for windows and Epi info2000 software. Age and sex specific incidence rates were calculated and plotted. Age-adjusted incidence rates were calculated using the world standard population. The incidence rate was compared from 1981 to 2001 using the χ2 trends test and the χ2 test was used to compare the average incidence rate. The age at diagnosis was compared employing the t-test. ## RESULTS ### Histological type Data from the cancer incidence reporting cards during the period of 1981∼2001 showed that 756 cases had thyroid pathological results, accounting for about 57.4% of all thyroid cases. Papillary adenocarcinoma was the most common type. There was no significant difference in the histological type between males and females (Table 1). View this table: [Table 1.](http://www.cancerbiomed.org/content/2/5/815/T1) Table 1. Constituent ratio (CR) of the histological type of thyroid cancer in Tianjin, 1981-2001 (%) ### Age and sex constitution at diagnosis A total of 1,318 cases of thyroid cancer were identified in Tianjin between 1981 and 2001 with 352 cases occurring in males and 966 cases in females. The male: female incidence ratio was 1:2.74. The incidence was the highest in the 60∼65 age groups for males and in the 35∼50 age groups for females. The median age at diagnosis was 50 years, being 55 and 49 years for males and females respectively. The age of onset occurred earlier in females than in males (t=3.01, *P=* 0.0026). ### Incidence and time trend The total average incidence rate of thyroid carcinomas was 1.770 per 100,000 in the Tianjin urban area during the 1981∼2001 period. The incidence rate increased from 0.869 per 100,000 in 1981 to 2.543 per 100,000 in 2001, an increase of 193% during the entire period. The incidence rate showed a statistically significant elevation trend over this period Table 2. The rank of thyroid cancer incidence also climbed from 22 in 1981 to 17 in 2001. View this table: [Table 2.](http://www.cancerbiomed.org/content/2/5/815/T2) Table 2. Thyroid cancer incidence rate in Tianjin during recent 21 years(l/100,000). ### Age and sex-specific incidence trend During the 1981∼2001 periods, the average thyroid cancer incidence rate was 0.938 per 100,000 for males, and showed an increase of 99.12% over those years. The average incidence rate was 2.615 per 100,000 for females, and from 1981∼2001 it increased from 1.296 to 4.187 per 100,000, an elevation of 223%. Females had consistently higher incidence rates compared to males across all age groups during this period (χ2 =294.429, P=0.000). Moreover the magnitude of incidence increase was greater in females Fig.1. The mean male:female incidence ratio was 1:2.74 in 1981 and 1:4.59 in 2001. ![Fig. 1.](http://www.cancerbiomed.org/https://www.cancerbiomed.org/content/cbm/2/5/815/F1.medium.gif) [Fig. 1.](http://www.cancerbiomed.org/content/2/5/815/F1) Fig. 1. Thyroid cancer incidence time trend by sex during 1981∼2001 in Tianjin. The patterns of age-specific incidence differ significantly by gender. Incidence rates in females climbed steeply after 25 years of age and through the reproductive years, gradually leveling off at about age 45, but then rose quickly again from age 60, increasing slightly after 65. Male incidence rates simply increased gradually with increasing age (Fig.2). ![Fig. 2.](http://www.cancerbiomed.org/https://www.cancerbiomed.org/content/cbm/2/5/815/F2.medium.gif) [Fig. 2.](http://www.cancerbiomed.org/content/2/5/815/F2) Fig. 2. Thyroid cancer age-specific incidence rate during 1981-2001 in Tianjin. ## DISCUSSION ### Incidence trend Thyroid cancer is one of the most common malignant tumors in women of childbearing age, although overall it is a rare malignancy. In many parts of China, it often ranks first in entire head and neck cancers.[1] Data from Surveillance, Epidemiology, and End Results (SEER) reports from the National Cancer Institute showed that the thyroid cancer incidence rate in the U.S. increasedfrom 6.4/100,000 in 1975 to 11.7/100,000 in 2001 for females, and from 3.1/100,000 to 4.2/100,000 for males.[2] Thyroid cancer showed one of the biggest increases in malignant tumors during the period of 1978∼2001 in France.[3] In a 1990 report from Norway, the annual incidence rate of thyroid cancer in females increased over the 1970-1985 period.[4] The statistical results among the most recent 20 years in Tianjin also indicated the same trend. It has been suggested that the gradual improvement of medical diagnosis might be responsible for this increasing trend. It is interesting that the thyroid incidence rate is higher in developed countries compared to developing countries and dis tricts in the IARC reports.[5] Our study is consistent with previous research. ### Sex and age distribution The report of cancer incidence in 5 continents from the IARC showed that the thyroid cancer incidence rate has increased with age in the entire world and was higher in females than males. The male: female incidence ratio was about 1:3 and has reached a peak at 45 years or so in females.[5] It is reported from New Mexi co that thyroid cancer occurs 2 to 3 times more fre quently in females than in males. The patterns of age-specific incidence also differ significantly by gen der. Incidence rates in females climb steeply after pu berty and through the reproductive years, gradually leveling off at about age 40 and then declining slightly after age 75. Male incidence rates simply increase gradually with increasing age, leading to an almost equal sex ratio among the elderly[6] Gender and age distribution of thyroid cancer was similar for Tianjin and the U.S. However in Tianjin, the incidence rate increased higher in females. Perhaps this finding was related to improved diagnostic ability and obesity and the fluctuation of female hormone levels induced by higher living standards and other correlation diseases such as bengin thyroid nodules. Moreover the age-specific incidence curve for females increased sharply from puberty, reaching a plateau after age 40 to 45, after which it peaked in 65 age group, and remained high thereafter. It is thus clear that thyroid cancer occurred more widely in females in Tianjin compared to males, including the whole fertile parts of life. This may be related to the higher iodine intake resulting from the geographical situation of Tianjin which is along the coast. Further investigations on risk factors are needed to determine the cause of the increase in incidence of thyroid cancer in the female population. ### Regional distribution According to the 2000IARC report, the world-wide thyroid cancer incidence rate in males and in females was 1.2/100,000 and 3.0/100,000 respectively. The countries and districts with a higher incidence rate were Polynesia, Ice land, Italy, Israel, Finland, Hong Kong, Canada, USA etc; China belongs to the low-incidence region.[5] Our results indicated that the thyroid cancer standard incidence rate according to world population adjusted was 1.422/100,000. ### Prevention strategy The etiological factors of thyroid cancer, like other cancers, are still obscure. Some researches have shown an enormous elevation of thyroid cancer among the population who lived in the radiated regions after the Chernobyl accident.[7-10] It has been suggested that radiation treatment in the head and neck for benign childhood conditions may be responsible for the observed increase of thyroid cancer.[11] So exposure to high-dose ionizing radiation could one of the important etiological factors for thyroid cancer, however, such exposures account for a minority of overall cases. Other risk factors include a personal history of benign thyroid nodules, family history of thyroid cancer, obesity and certain reproductive and hormonal factors in women [12]. Although some reports have emphasized that sex hormones may influence thyroid carcinogenesis,[13,14] these relationships warrant further investigation. Thyroidstimulating hormone (TSH) receptor may be involvedˆ>B in the carcinogenic process. [12,15] Molecular studies have indicated that some oncogenes and growth factors are involved in thyroid carcinogenesis.[1,12] However no clear preventative measures or control methods are known. Therefore the approach to fight thyroid cancer is still based on the principles of early detection, early diagnosis and early treatment. Thyroid benign diseases should be treated quickly. Although the thyroid cancer incidence is not as high as other tumors, its increasing trend in recent years is of great concern. In summary, data based on the thyroid cancer incidence shows the incidence rate has been growing year by year; especially over the 20 year period studied the incidence trend in females has shown a sharp increase. In addition the incidence ratio of females: males was also shown to be augmented year by year, and in particular, younger women showed increased risk. So not only is there a great need to study risk factors so that preventative measures can be applied, but also there is the need for educating women in the 35-50 age group who are at particular increased risk. Regular self-examinations and checkups should be advocated to increase early diagnosis and the proportion of patients who receive early therapy, so that the quality of life for women in reproductive ages is improved. * Received August 13, 2004. * Accepted September 14, 2005. * Copyright © 2005 by Tianjin Medical University Cancer Institute & Hospital and Springer ## References 1. Li SL. Head and Neck Oncology. Tianjin. Tianjin Science Technology Press.1993; 717–756. 2. Jemal A, Clegg LX, Ward E, et al. Annual Report to the Nation on the Status of Cancer, 1975∼2001, with a Special Feature Regarding Survival. Cancer. 2004; 101: 3–27. [CrossRef](http://www.cancerbiomed.org/lookup/external-ref?access_num=10.1002/cncr.20288&link_type=DOI) [PubMed](http://www.cancerbiomed.org/lookup/external-ref?access_num=15221985&link_type=MED&atom=%2Fcbm%2F2%2F5%2F815.atom) [Web of Science](http://www.cancerbiomed.org/lookup/external-ref?access_num=000222134200002&link_type=ISI) 3. Remontet L, Esteve J, Bouvier AM. Cancer incidence and mortality in France over the period 1978-2000. Rev Epidemiol Sante Publique. 2003; 51: 3–30. [PubMed](http://www.cancerbiomed.org/lookup/external-ref?access_num=12684578&link_type=MED&atom=%2Fcbm%2F2%2F5%2F815.atom) [Web of Science](http://www.cancerbiomed.org/lookup/external-ref?access_num=000182301200002&link_type=ISI) 4. Akslen LA, Haldorsen T, Thoresen SO, et al. Incidence of thyroid cancer in Norway 1970-1985. Population review on time trend, sex, age, histological type and tumour stage in 2625 cases. APMIS. 1990; 98: 549–558. 5. Ferlay J, Bray F, Pisani P, et al. GLOBOCAN 2000. Cancer Incidence, Mortality and Prevalence Worldwide. IARC Press. Lyon 2001. 6. Athas WF. Cancer in New Mexico: Changing patterns and emerging trends, 1970-1996. New Mexico Tumor Registry. 1998; 98–101. 7. Tai P, Mould R, Prysyazhnyuk A, et al. Descriptive epidemiology of thyroid carcinoma. Curr Oncol. 2003; 10: 54–65. 8. Zhumadilov Z, Gusev BI, Takada J, et al. Thyroid abnormality trend over time in northeastern regions of Kazakstan, adjacent to the Semipalatinsk nuclear test site: a case review of pathological findings for 7271 patients. J Radiat Res. 2000; 41: 35–44. [CrossRef](http://www.cancerbiomed.org/lookup/external-ref?access_num=10.1269/jrr.41.35&link_type=DOI) [PubMed](http://www.cancerbiomed.org/lookup/external-ref?access_num=10838808&link_type=MED&atom=%2Fcbm%2F2%2F5%2F815.atom) 9. Ivanov VK, Tsyb AF, Nilova EV, et al. Cancer risks in the Kalugaoblast of the Russian Federation 10 years after the Chernobyl accident. Radiat Environ Biophys. 1997; 36: 161–167. [CrossRef](http://www.cancerbiomed.org/lookup/external-ref?access_num=10.1007/s004110050067&link_type=DOI) [PubMed](http://www.cancerbiomed.org/lookup/external-ref?access_num=9402632&link_type=MED&atom=%2Fcbm%2F2%2F5%2F815.atom) [Web of Science](http://www.cancerbiomed.org/lookup/external-ref?access_num=A1997YJ54400003&link_type=ISI) 10. Szybinski Z, Huszno B, Zemla B, et al. Incidence of thyroid cancer in the selected areas of iodine deficiency in Poland. J Endocrinol Invest. 2003; 26: 63–70. [PubMed](http://www.cancerbiomed.org/lookup/external-ref?access_num=12762643&link_type=MED&atom=%2Fcbm%2F2%2F5%2F815.atom) 11. Zheng T, Holford TR, Chen Y, et al. Time trend and ageperiod-cohort effect on incidence of thyroid cancer in Connecticut, 1935-1992. Int J Cancer. 1996; 67: 504–509. [CrossRef](http://www.cancerbiomed.org/lookup/external-ref?access_num=10.1002/(SICI)1097-0215(19960807)67:4<504::AID-IJC7>3.0.CO;2-W&link_type=DOI) [PubMed](http://www.cancerbiomed.org/lookup/external-ref?access_num=8759608&link_type=MED&atom=%2Fcbm%2F2%2F5%2F815.atom) [Web of Science](http://www.cancerbiomed.org/lookup/external-ref?access_num=A1996VA33800007&link_type=ISI) 12. Adami HO, Hunter D, Trichopoulos D. Textbook of Cancer Epidemiology. New York. Oxford University Press.2002; 504–519. 13. Lundgren CI, Hall P, Ekbom A, et al. Incidence and survival of Swedish patients with differentiated thyroid cancer. Int J Cancer. 2003; 106: 569–73. [CrossRef](http://www.cancerbiomed.org/lookup/external-ref?access_num=10.1002/ijc.11275&link_type=DOI) [PubMed](http://www.cancerbiomed.org/lookup/external-ref?access_num=12845654&link_type=MED&atom=%2Fcbm%2F2%2F5%2F815.atom) [Web of Science](http://www.cancerbiomed.org/lookup/external-ref?access_num=000184672300017&link_type=ISI) 14. Sakoda LC. Horn-Ross PL. Reproductive and menstrual history and papillary thyroid cancer risk: The San Francisco Bay area thyroid cancer study. Cancer Epidemiol Biomarkers Prev. 2002; 11: 51–57. 15. Pujol P, Daures JP, Nsakalan N, et al. Degree of thyrotropin suppression as a prognostic determinant in differentiated thyroid cancer. J Clin Endocrinol Metab.1996; 81: 4318–4323. [CrossRef](http://www.cancerbiomed.org/lookup/external-ref?access_num=10.1210/jc.81.12.4318&link_type=DOI) [PubMed](http://www.cancerbiomed.org/lookup/external-ref?access_num=8954034&link_type=MED&atom=%2Fcbm%2F2%2F5%2F815.atom) [Web of Science](http://www.cancerbiomed.org/lookup/external-ref?access_num=A1996VW46200022&link_type=ISI)