Pre‐op Thyroglobulin and Sentinel Lymph Node Biopsy Outcomes

Abstract

Objective: 1) To retrospectively assess the usefulness of preoperative thyroglobulin (Tg) levels in predicting sentinel lymph node (SLN) biopsy (SLNB) status. 2) To evaluate the correlation between preoperative Tg levels and the overall number of positive SLNs. 3) To compare primary tumor (T) classification in patients according to SLNB outcome. Method: Data from patients operated for well-differentiated thyroid carcinoma (WDTC) at the McGill University Thyroid Cancer Center were collected from January 2007 to January 2012. Statistical analyses were performed using a Mann-Whitney-Wilcoxon test, a Pearson correlation coefficient and a Pearson χ2 test. Results: Preoperative Tg levels and SLNB results were available in 74 patients (51 negative and 23 positive SLNBs). Mean preoperative Tg levels for negative and positive SLNB groups were 105.2 and 85.9 ng/mL, respectively, yielding no statistically significant difference ( P = .143). Moreover, no statistically significant correlation was found between Tg levels and the number of positive SLNs ( P = .515). While 82.4% of patients with negative SLNBs had a T1 or T2 class WDTC, 82.6% of patients with positive SLNBs had a T3 or higher class, yielding a statistically significant difference between the 2 groups ( P < .001). Conclusion: Preoperative Tg levels are not significantly different in patients with positive SLNBs as compared to negative SLNBs, and show no significant correlation with the number of positive SLNs. Thus, an elevated preoperative Tg is not a predictor of SLN status. Patients with positive SLNBs, however, have significantly worse T classifications.