Trends in the Clinical Characteristics of Patients with Papillary Thyroid Carcinoma in Taiwan

Abstract

The incidence of thyroid cancer is influenced by many factors including socioeconomic status. As economic conditions have improved in Taiwan, the increased frequency of medical examinations in the general population has led to earlier diagnosis of this indolent malignancy. The purpose of this retrospective study was to compare the clinical characteristics of cases of papillary thyroid cancer diagnosed over a 6-year period from 1993 to 1998 with those patients diagnosed from 1977 to 1992 at a single medical center. Of the 1,485 pathologically verified cases of thyroid cancer from 1977 to 1998, 1,093 had papillary thyroid carcinoma. The mean age of these patients was 40.4 ± 14.6 years. In order to identify trends in the characteristics of patients with thyroid cancer, patients were divided into those diagnosed before and those diagnosed after 1993. Patients diagnosed in these two time periods were also categorized into disease-free or non-disease-free groups depending on their status at the end of 1998. Actuarial survival rates were calculated using the Kaplan-Meier method. Multivariate analysis was performed to assess the independent effect of these variables using the Cox model. By December 1998, 61 (5.6%) of the 1,093 patients with papillary thyroid carcinoma had died. Among them, only 35 (3.2%) patients had died of thyroid cancer. The 5-year Greenwood survival probabilities for the groups diagnosed before and after 1993 were 0.9412 and 0.9817, respectively. The patients diagnosed after 1993 received more aggressive surgical procedures, had smaller tumor size, lower postoperative thyroglobulin levels, less advanced clinical stage at the time of diagnosis, showed more disease-free survival, and a lower mortality rate. In conclusion, the results of this study show that patients with a diagnosis of papillary thyroid cancer after 1993 had a smaller tumor size and a better prognosis than those diagnosed before 1993. This finding emphasizes the importance of early detection in thyroid cancer.