Age greater than 60 years portends a worse prognosis in patients with papillary thyroid cancer: should there be three age categories for staging?

BACKGROUND: Age is an important prognostic factor in papillary thyroid cancer (PTC), with better survival observed in patients < 45 years of age, regardless of stage. Although the impact of increasing age on PTC-related survival is well-known, previous studies have focused on survival relative to age 45 years only. As the number of patients entering their 7th decade of life increases, PTC-related survival in this demographic becomes increasingly important. Survival in patients ≥ 60 years specifically compared to other groups has not previously been examined. We sought to determine whether age ≥ 60 years is an adverse prognostic factor for disease-specific survival and recurrence in patients with PTC. METHODS: The California Cancer Registry database was linked to inpatient and ambulatory patient records from the Office of Statewide Health Planning and Development for the years 2000–2011. This linked database was queried for patients diagnosed with papillary thyroid cancer and treated with surgery. We then identified prognostic factors related to both 5-year and 10-year disease-specific survival and disease-free survival in patients ≤ 45, 45–59, and ≥ 60 years. Multivariable Cox proportional hazard models were created to test the effect of age ≥ 60 on disease-specific and disease-free survival, controlling for clinical, treatment, and demographic factors. RESULTS: The final cohort included 15,675 patients. Of the group, 46.3% were between 18 and 44 years of age, 33.6% were 45–59 years, and 20.1% were ≥ 60. Univariate analysis showed that compared to other groups, patients ≥ 60 were more likely to be male (p < 0.001), present with tumors > 5 cm (p < 0.001), more likely to have metastatic disease (p < 0.001), less likely to receive radioactive iodine (p < 0.001), and more likely to receive external beam radiation therapy (p < 0.001). In multivariable Cox proportional hazards models for 5 and 10-year disease-free survival, age ≥ 60 was associated with higher risk of disease at 5 and 10-years (HR 2.3 and 1.9 respectively, p < 0.001). Similar results were observed for 5 and 10-year disease-specific survival (HR 38.0 and 30.0 respectively, p < 0.001) after controlling for gender, race, co-morbidity, stage, surgical procedure, radioactive iodine, insurance, and hospital volume. CONCLUSIONS: Patients ≥ 60 years of age have worse DSS and DFS after a diagnosis of PTC, across all stages of disease. Given that patients over the age of 45 years have progressively worse survival as they age, these data support having three age groups, 18–44 years of age, 45–59 years, and ≥ 60 as an independent predictor of survival and recurrence to current staging guidelines.