Endocrine Abstracts

Background: Whether sitagliptin use in patients with type 2 diabetes mellitus may affect the risk of thyroid cancer requires further investigated.

Methods: The reimbursement database of the National Health Insurance in Taiwan was used. Patients with newly diagnosed type 2 diabetes mellitus within 1999–2008 were recruited and followed for at least 6 months for thyroid cancer until December 31, 2011. Patients were divided into those who were newly treated with sitagliptin (n=50045, “ever users of sitagliptin”) or other antidiabetic drugs (n=277100, “never users of sitagliptin”). The treatment effect of sitagliptin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score.

Results: The respective numbers of incident thyroid cancer in ever users and never users were 25 (0.05%) and 152 (0.05%), with respective incidences of 30.34 and 22.04 per 100 000 person-years. The overall hazard ratios (95% confidence intervals) suggested a significantly higher risk (1.573 (1.025, 2.414)). In tertile analyses, the hazard ratios (95% confidence intervals) for the first (<6.53 months), second (6.53–14.00 months) and third (>14 months) tertile of cumulative duration were 2.098 (1.025, 4.295), 2.476 (1.368, 4.483) and 0.689 (0.283, 1.682), respectively. Sensitivity analyses after excluding patients with benign thyroid disease at baseline showed similar results.

Conclusions: Sitagliptin use is associated with an increased risk of thyroid cancer, especially during the first year of its treatment. The increased risk within a short-term of cumulative duration of exposure probably precludes a mechanism involving de novo development of thyroid cancer. Future studies are required to confirm the findings of the present study.