Stage II differentiated thyroid cancer: A mixed bag.

BACKGROUND AND OBJECTIVES: AJCC-TNM Stage II well-differentiated thyroid cancer (WDTC) comprises T2N0M0 tumors in patients ≥45 years of age or metastatic WDTC in patients younger than 45 years. The objectives of this study were to assess the oncological outcome of stage II WDTC and to compare the oncological outcome of metastatic WDTC in patient younger (stage II) and older (stage IVC) than 45 years. METHODS: This study involved review of clinical presentation and oncological outcome of population cohort of 2,128 consecutive WDTC, diagnosed during 1970-2010 that includes 215 Stage II WDTC and 61 metastatic WDTC. Cox proportional hazard model was used to assess independent impact of prognostic factors on disease-specific survival (DSS) and disease-free survival (DFS) as calculated by Kaplan-Meier method. RESULTS: Metastatic and non-metastatic stage II WDTC had a 15-year DSS of 41.7% and 96.7%, respectively (P < 0.001). Multivariable analysis showed a 52 times higher risk of death in metastatic stage II WDTC and the DSS of metastatic stage II WDTC was not statistically different from that of stage IVC WDTC. CONCLUSION: Metastatic stage II WDTC is very different from non-metastatic stage II WDTC with oncological outcome similar to stage IVC WDTC.

The changing face of thyroid cancer in a population-based cohort.

In North America, the incidence of thyroid cancer is increasing by over 6% per year. We studied the trends and factors influencing thyroid cancer incidence, its clinical presentation, and treatment outcome during 1970-2010 in a population-based cohort of 2306 consecutive thyroid cancers in Canada, that was followed up for a median period of 10.5 years. Disease-specific survival (DSS) and disease-free survival were estimated by the Kaplan-Meier method and the independent influence of various prognostic factors was evaluated by Cox proportional hazard models. Cumulative incidence of deaths resulting from thyroid cancer was calculated by competing risk analysis. A P-value <0.05 was considered to indicate statistical significance. The age standardized incidence of thyroid cancer by direct method increased from 2.52/100,000 (1970) to 9.37/100,000 (2010). Age at diagnosis, gender distribution, tumor size, and initial tumor stage did not change significantly during this period. The proportion of papillary thyroid cancers increased significantly (P < 0.001) from 58% (1970-1980) to 85.9% (2000-2010) while that of anaplastic cancer fell from 5.7% to 2.1% (P < 0.001). Ten-year DSS improved from 85.4% to 95.6%, and was adversely influenced by anaplastic histology (hazard ratio [HR] = 8.7; P < 0.001), male gender (HR = 1.8; P = 0.001), TNM stage IV (HR = 8.4; P = 0.001), incomplete surgical resection (HR = 2.4; P = 0.002), and age at diagnosis (HR = 1.05 per year; P < 0.001). There was a 373% increase in the incidence of thyroid cancer in Manitoba with a marked improvement in the thyroid cancer-specific survival that was independent of changes in patient demographics, tumor stage, or treatment practices, and is largely attributed to the declining proportion of anaplastic thyroid cancers.