Abstract
Well-differentiated thyroid carcinoma (WDTC) represents a group of thyroid cancers with excellent prognosis. Age, a well-recognized risk factor for WDTC, has been consistently included in various prognostic scoring systems. An age threshold of 45 years is currently used by the American Joint Cancer Committee-TNM staging system for the risk stratification of patients. This study analyzes the relationship between the patients' age at diagnosis and thyroid cancer-specific survival in a population-based thyroid cancer cohort of 2115 consecutive patients with WDTC, diagnosed during 1970–2010, and evaluates the appropriateness of the currently used age threshold. Oncological outcomes of patients in terms of disease-specific survival (DSS) and disease-free survival (DFS) were calculated by the Kaplan–Meier method, while multivariable analysis was done by the Cox proportional hazard model and proportional hazards regression for sub-distribution of competing risks to assess the independent influence of various prognostic factors. The mean age of the patients was 47.3 years, 76.6% were female and 83.3% had papillary carcinoma. The median follow-up of the cohort was 122.4 months. The DSS and DFS were 95.4 and 92.8% at 10 years and 90.1 and 87.6% at 20 years, respectively. Multivariable analyses confirmed patient's age to be an independent risk factor adversely affecting the DSS but not the DFS. Distant metastasis, incomplete surgical resection, T3/T4 stages, Hürthle cell histology, and male gender were other independent prognostic determinants. The DSS was not independently influenced by age until the age of 55 years. An age threshold of 55 years is better than that of 45 years for risk stratification.
Highlights
Well-differentiated thyroid carcinoma (WDTC) represents a group of thyroid cancers that are associated with increasing incidence and excellent posttreatment outcome [1]
On January 1, 2013, 1658 (78.5%) patients had no evidence of disease; 49 (2.3%) patients were alive with disease; 105 (5.0%) patients were dead because of thyroid cancer; 78 (3.7%) patients had died of a second primary tumor; and 225 (10.6%) patients died of other causes
Three (0.1%) patients who had a synchronous medullary or poorly differentiated carcinoma were excluded from further analysis as these synchronous malignancies were thought to be more aggressive than their papillary thyroid cancer
Summary
Well-differentiated thyroid carcinoma (WDTC) represents a group of thyroid cancers that are associated with increasing incidence and excellent posttreatment outcome [1]. This group comprises different histological types, the most common being papillary carcinoma, followed by follicular carcinoma, and Hurthle cell variant of follicular carcinoma [2]. Several factors have been associated with aggressive behavior in WDTC, including the age at diagnosis, the gender of the patient, the size and extension of the primary tumor, and the presence of distant metastases [1, 2, 3, 4, 5]
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