Secular trends study on the incidence and constituent ratio of papillary thyroid cancer in Tianjin        QIAN Bi-yun, HE Min, CHEN Ke-xin, et al. Tianjin Medical University Cancer Institute and Hospital, Tianjin Key Laboratory of Cancer Prevention, Tianjin 300060，China
Corresponding author：GAO Ming，E-mail: gming68@yahoo.com.cn
Abstract    Objective    To analyze the incidence of papillary thyroid cancer (PTC) between 1981 and 2006 in Tianjin. Methods    Descriptive epidemiological methods were conducted. The crude incidence rate, sex, age-specific incidence rate and the constituent ratio in thyroid cancer were computed. Annal percent change (APC%) of the PTC incidence for 26 years old was estimated by the Joinpoint regression model. Results    The incidence of PTC was 1.30/100,000 between 1981 and 2006 and 2.14/100,000 in female. APC of PTC was 6.7% in recent 26 years, which was more than the speed of thyroid cancer. The incidence of PTC in female was higher than that in male, which showed a 4.4 fold increase with 0.87/100,000 in 1981 and 4.70/100,000 in 2006. APC of PTC in female was 6.2%. The constituent ratio of PTC in thyroid cancer increased from 11.1% in 1981 to 69.5% in 2006, with a 5.3 fold increase. The sex ratio of the incidence for female to male showed a peak on the 20-49 years old. Conclusion    The incidence and constituent ratio of PTC in female show a rapidly increased tendency with time in recent years, especially in the peak of sex ratio on the specific age group. It suggests that further researches on the risk factors and preventive efforts should be made in the future.