Disease-Specific Mortality and Secondary Primary Cancer in Well-Differentiated Thyroid Cancer with Type 2 Diabetes Mellitus

Background: Increased body mass index is related to the incidence of thyroid cancer. However, the presentation and therapeutic outcomes of different thyroid cancers and type 2 diabetes mellitus (DM) have not been studied. This study investigated the effect of type 2 DM on the clinical presentations and therapeutic outcome of well-differentiated thyroid cancer. Methods and Findings: A retrospective analysis of adult thyroid cancer patients with or without type 2 DM admitted between January 2001 and December 2010 was performed at an institution. A total of 1,687 well-differentiated thyroid cancer patients with different histological patterns were enrolled. Among these subjects, 122 were type 2 DM patients. Patients with thyroid cancer and type 2 DM were significantly older than non-DM patients. After a mean follow-up period of 5.660.1 years, patients with thyroid cancer and type 2 DM showed a higher percentage of disease progression than non-DM patients (24.6 % vs. 17.4%). In addition, disease-specific mortality was higher in the type 2 DM group (10.7 % vs. 3.8%). Thyroid cancer patients with type 2 DM showed a higher percentage of secondary primary cancers than those without DM (10.7 % vs. 4.9%). Thyroid cancer-specific survival rates in the type 2 DM and non-DM groups were 82.2 % and 94.9 % at 5 years, 72.9 % and 91.4 % at 10 years, and 36.5 % and 61.3 % at 20 years, respectively. Multivariate analysis showed that type 2 DM was independent of thyroid cancer-specific mortality