Prognostic significance and optimal cutoff of age in medullary thyroid cancer

Age has been found to correlate with the prognosis for medullary thyroid cancer (MTC). This study was conducted to investigate whether age can predict long-term unfavorable prognosis and evaluate its predictive accuracy associated with TNM staging, using data of patients diagnosed with MTC between 2000 and 2010 from Surveillance, Epidemiology and End Results database. The relationship between the patients’ age at diagnosis and cancer-specific survival (CSS) was evaluated using multivariate Cox regression analysis. Age stratifications were combined into a nomogram model to predict the CSS of MTC. The X-tile program determined 49 and 69 as optimal age cutoff values for CSS. On multivariate analysis, independent factors for survival were age (50–69 years, HR 2.853, 95% CI 1.631–4.991; ≥70 years, HR 5.804, 95% CI 2.91–11.555), race (white, HR 0.344, 95% CI 0.188–0.630), T (T3/4, HR 3.931, 95% CI 2.093–7.381), N (N1a, HR 3.269, 95% CI 1.386–7.710) and M (M1, HR 3.998, 95% CI 2.419–6.606). The C-index for CSS prediction with TNM, age (cutoff of 45)/sex/race/TNM and age (cutoff of 49 and 69)/sex/race/TNM were 0.832 (95% CI 0.763–0.901), 0.863 (95% CI 0.799–0.928), and 0.876 (95% CI 0.817–0.935), respectively. Subgroup multivariate analyses also showed that age significantly increased the risk for CSS in females, non-Hispanic white patients, and those with stage IV MTC. In conclusion, CSS was independently associated with ages between 49 and 69 years, which might be applied for risk stratification in MTC patients.