Insulin resistance is another factor that increases the risk of recurrence in patients with thyroid cancer.

The objective of this study was to evaluate the initial response to treatment and the long-term outcome of patients with papillary thyroid cancer (PTC), according to the modified 2014 risk of recurrence classification of the American Thyroid Association and the presence or absence of insulin resistance (IR). We retrospectively reviewed our database of 636 records and selected 171 patients in whom we had previously validated the ATA risk of recurrence (RR) classification. From these patients, 38 non-diabetic subjects were included for analysis according to the following criteria: age older than 18 years, classic papillary thyroid carcinoma, stable body mass index 5 years previous to PTC diagnosis and during the entire time of follow-up, low and intermediate RR, follow-up after initial treatment at least for 3 years, and absence of any drug treatment for the metabolic syndrome. The IR was evaluated through the homeostasis model assessment (HOMA) index. When equal or higher than 2.5, patients were considered as harboring IR. The initial response to treatment was classified as remission or persistent disease (biochemical and/or structural). The clinical status at final follow-up was defined as no evidence of disease, biochemical persistent disease, structural persistent disease, or recurrence (biochemical or structural disease identified after a period of no evidence of disease). RR was as follows: low: n=15, intermediate: n=23. The median follow-up of this patient cohort was 5.5 years (range 3-22 years). We found no statistically significant differences when the response to initial treatment was considered in low-risk patients with or without IR. However, remission was more frequently found in those patients without IR when the intermediate RR was considered (36 vs. 11%, p=0.01). When considering the status at final follow-up, we found more frequency of structural persistent disease in both, low and intermediate RR patients with IR (10 vs. 0%, p=0.02 and 45 vs.7%, p=0.01, respectively). In this series of patients with PTC, the state of IR was associated with increased frequency of structural persistent disease at final follow-up. The IR could have a deleterious effect on the outcome of patients with PTC.