Secular trends in the prognostic factors for papillary thyroid cancer

Abstract

Objective: With the recent increasing rates of screening for thyroid cancer, the cancers now tend to be smaller and less aggressive than those that are diagnosed when presented with symptoms, suggesting changes in the clinical validity of conventional prognostic factors for outcomes. We performed the retrospective study to identify the secular trends in the prognostic factors of thyroid cancer. Methods: We used medical records of 3147 patients diagnosed with papillary thyroid cancer (PTC) at the Seoul National University Hospital Thyroid Cancer Clinic between 1962 and 2009. Results: During the median 5.1-year follow-up, the overall recurrence rate was 13.3%, and male sex, tumor size, lymph node (LN) involvement, and extrathyroidal extension (ETE) were the significant prognostic factors for recurrence. Thyroid cancer-specific mortality was 1.4%, and the associated prognostic factors were older age, male sex, and LN involvement. For tumor recurrence, the hazard ratio (HR) for male sex decreased from 2.809 (95% CI, 1.497-5.269) in the pre-1989 period to 1.142 (95% CI, 0.736-1.772) in the post-1999 period. The pathologic characteristics, such as tumor size, LN involvement, and ETE, showed similar or increasing HRs over the time periods. For cancer-specific mortality, the HR for male sex decreased from 6.460 (95% CI, 1.714-24.348) in the pre-1990 period to 0.781 (95% CI, 0.083-7.379) in the post-1999 period. Conclusion: The risk for poor outcomes in PTC associated with male sex decreased over time; in contrast, the risk associated with pathologic characteristics remained the same or increased over time. These trends might be associated with recent changes in the characteristics of patients with thyroid cancer.