Effect of Age on Response to Therapy and Mortality in Patients With Thyroid Cancer at High Risk of Recurrence

Context Age at diagnosis has been identified as a major determinant of thyroid cancer–specific survival, with older patients being at higher risk for mortality, but the association of age with risk of recurrence has not been studied to date. Objective To examine the effect of a patient’s age on response to therapy and disease-specific mortality in a cohort of thyroid cancer patients at high risk of recurrence, as defined by the American Thyroid Association (ATA) risk stratification system. Design Retrospective cohort study of 320 patients, median age 49.3 years, with follicular cell-derived thyroid carcinoma classified at ATA high risk and followed for a median of 7 years. Main Outcome Measures Association of age with response to therapy, overall mortality, disease-specific mortality, and timing of metastases. Results Age was a major determinant of response to therapy. There was a significantly larger percentage of excellent responders among young patients (age <55) than among old patients (age ≥55), 40.3% vs 27.5%, P = 0.002, respectively, whereas the proportion of structural incomplete responders was higher in the old group compared with the young group, 53% vs 33%, P = 0.002, respectively. ATA high-risk young patients with a structural incomplete response to therapy had a significantly better disease-specific survival than old patients (74% vs 12%, P < 0.001, respectively). Conclusions Age was a key predictor of response to therapy and disease-specific survival in ATA high-risk thyroid cancer patients. Its incorporation as a variable in the ATA risk stratification system would improve its power to predict response to therapy as well as mortality.