Impact of glycated hemoglobin (HbA1c) on outcomes in differentiated thyroid cancer with type 2 diabetes mellitus

Introduction: Type 2 diabetes mellitus (T2DM) is a frequent comorbidity in differentiated thyroid cancer (DTC). This study evaluated the impact of glycemic control, particularly glycated hemoglobin (HbA 1c ) levels, on tumor characteristics and treatment outcomes. Material and methods: We retrospectively analyzed 302 DTC patients, including 58 (19.2%) with T2DM. Baseline demographic, clinical, and pathological data were collected. Treatment response was assessed as per American Thyroid Association (ATA) guidelines. Logistic regression identified predictors of non-excellent response, and a subgroup analysis was performed among diabetic patients stratified by HbA 1c (< 7% vs. ≥ 7%). Results: T2DM patients were older (p < 0.001), with more bilateral tumors (p = 0.047) and higher tumor foci (p = 0.039). Other tumor features were similar between groups. In multivariate analysis, both HbA 1c [odds ratio (OR): 1.307, 95% confidence interval (CI): 1.014–1.683, p = 0.038) and lymph node metastasis (OR: 3.932, 95% CI: 1.000–15.464, p = 0.050] independently predicted non-excellent response. Among diabetics, HbA 1c ≥ 7% was associated with higher non-excellent response rates (p = 0.030). Conclusion: Poor glycemic control, rather than T2DM itself, was linked to suboptimal treatment response. HbA 1c may serve as a simple prognostic marker in diabetic patients with DTC.