Assessing the utility of preoperative serum thyroglobulin in differentiated thyroid cancer: a retrospective cohort study.

PURPOSE

Serum thyroglobulin (TG) is used to monitor for recurrence or progression of differentiated thyroid cancer (DTC). The role of preoperative TG measurement is more ambiguous, yet still being used in some centers. We aimed to determine whether preoperative TG correlates with disease stage or metastatic burden.

METHODS

A retrospective review of patients with TG measured before thyroidectomy was conducted. Data collected included demographics, preoperative TG, pathology, and cancer stage. Associations between preoperative TG levels and size of largest malignant nodule, thyroid gland size, stage of cancer, and presence of metastasis using Wilcoxon rank sum tests and Spearman correlations were performed. Receiver operator curve (ROC) was generated for metastasis status.

RESULTS

Of 598 patients, we excluded those with positive TG antibodies (n = 176); 422 patients were included in the final analysis. Median age was 55 years and 76% were female. Of 78% with malignancy, papillary thyroid cancer was the most frequent (92%). 18% had TG levels >500 ng/mL and 29% <45 ng/mL. 4% had distant metastasis and 18% had lymph node metastasis. Median follow-up was 52 months. Significant positive correlations between preoperative TG and thyroid size (rho 0.49, p < 0.001), and malignant nodule size (rho 0.27, p < 0.001). Using a cut-off of 500 ng/mL, sensitivity to detect metastasis was 10.3% (95% CI 2.5-18.2), specificity 90.0% (95% CI 86.0-93.9). The area under curve for ROC (0.46, 95% CI 0.38-0.54) indicated poor diagnostic ability for metastasis.

CONCLUSION

Although preoperative TG correlated significantly with the size of the gland and T stage, there was no correlation with metastasis. Preoperative TG is of limited utility in today's value-based healthcare environment.