Evaluation of Changes in Clinicopathological Features and Prognosis in Patients with Thyroid Cancer

<b>Background:</b> In this study, we evaluated the changes in clinicopathological features and prognosis in patients with thyroid cancer in the last two decades using the Surveillance, Epidemiology, and End Results Database (SEER) data. <b>Methods:</b> Data from the SEER-12 registry (1992-2021) were analyzed, focusing on patients diagnosed with malignant thyroid cancer between 2001 and 2020. The study population was divided into Cohort 1 (2001-2010) and Cohort 2 (2011-2020). Cohorts 1 and 2 were compared regarding clinicopathological features and prognosis. <b>Results:</b> The study included 94,892 patients diagnosed with thyroid cancer between 2001 and 2020, with 39,265 patients in Cohort 1 and 55,627 in Cohort 2. Compared to Cohort 1, in Cohort 2 showed a statistically significant increase in the proportion of patients aged 60+ (+4.2%), male patients (+2.1%), and cases of papillary cancer (+5.3%) and regional disease (+3.7%) (all <i>p</i> < 0.001). Although Cohort 2 demonstrated an 8% improvement in survival compared to Cohort 1, this result was not statistically significant (<i>p</i> = 0.057). Prognostic factors were identified, such as disease stage at diagnosis, age, gender, and origin. Among pathological subtypes, the patients with papillary + FV had the best prognosis (HR: 0.78), compared to patients in the other group, mainly comprising anaplastic tumors and sarcomas, which had the worst prognosis (HR: 9.61). <b>Conclusions:</b> In this large-scale study of thyroid cancer patients, we found significant differences between the two cohorts. In Cohort 2, the proportion of patients aged ≥60 years, male, and with papillary thyroid cancer was increased. We found that age, sex, origin, histopathological subtype, and stage at diagnosis were prognostic factors in patients with thyroid cancer. Also, we observed a trend toward improved survival in Cohort 2.