| Summary: | 碩士 === 國立臺灣大學 === 預防醫學研究所 === 96 === Background and purpose
The incidence rate of thyroid cancer has been increasing in recent years. While the prognosis of thyroid cancer is good, but there are still a fraction of the patients that eventually have poor prognosis. Thyroid ultrasound has been adopted for early detection of thyroid cancer, but the evidence is elusive. The aims of this study were to build a cohort of thyroid cancer and construct the multi-state natural disease history and multi-state treatment history of thyroid cancer to assess how natural progression of thyroid cancer evolves and how putative personal attributes and clinical attributes affect its natural course. Efficacy of thyroid ultrasound was further estimated by using two kinds of stochastic process.
Methods
This study was based on a hospital-based, non-standard case-cohort design. The cohort was composed of the patients with thyroid ultrasound in National Taiwan University Hospital after1985 and patients with thyroid cancers. The cases were randomly selected by different sampling ratios according to the status of thyroid cancer and survival. Multi-state Markov models of natural diseaase history and treatment history of thyroid cancer were constructed. Bayesian inversion tailor for non-standard case-cohort design was applied to identify significant factors responsible for each transition. The estimate of efficacy of thyroid ultrasound was done between the comparisons of different models. .
Main findings
In the natural disease history of thyroid cancer, the annual incidence rate from free of thyroid cance to ETC (echo-detectable thyroid cancer) was mainly affected by gender and age. Factors responsible for the transition between ETC and incurable stage included age of diagnosis, tumor size larger than 1 cm, the invasion of the extrathyroidal tissue, and the classification of thyroid cancer (medullary and follicular carcinoma). The transition between ETC and incurable differentiated thyroid cancer after treatment was affected by age of diagnosis, tumor size larger than 1 cm, and the invasion of the extrathyroidal tissue. Prognostic factors related to death from incurable differentiated thyroid cancer included age of diagnosis, medullary carcinoma and follicular carcinoma. Significant relevant factors pertaining to an anaplastic carcinoma or poorly differentiated thyroid cancer were male, age of diagnosis older more than 60 years old and the invasion of the extrathyroidal tissue. Significant factor for the transition anaplastic cancer or poorly differentiated thyroid cancer to death was was age of diagnosis between 40-60 years old. The efficacy of the ultrasound was 13% (95%CI:-25
-41%) in the arresting the procession from ETC to incurable thyroid cancer, and the efficacy was mainly in the prevention of well-differentiated thyroid cancer into anaplastic cancer or poorly differentiated thyroid cancer.
Conclusion
Non-standard case-cohort study together with a multi-state model is efficient in elucidating the natural history of thyroid cancer, significant factors related to natural course, and the efficacy.
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