Pre-ablation stimulated thyroglobulin is a better predictor of recurrence in pathological N1a papillary thyroid carcinoma than the lymph node ratio

Abstract

Background Papillary thyroid carcinomas (PTC) with lymph node metastases have a high recurrence rate. We analyzed the potential of lymph node ratio (LNR) and the level of pre-ablation stimulated thyroglobulin (sTg) as risk factors predicting recurrence in patients with pathological N1a PTC.

Materials and methods This study involved 192 patients with pathologically confirmed PTC and central neck lymph node metastases who underwent total thyroidectomy with central lymph node dissection (CLND). The clinico-pathological characteristics, the pre-ablation sTg level and post-treatment recurrences were examined. Univariate and multivariate analyses were performed to identify factors associated with recurrence in these patients.

Results During a median follow-up of 63 months, 17 patients had loco-regional recurrences. Receiver operating characteristic curve analysis showed that the appropriate cut-off values for LNR and the pre-ablation sTg level was 0.48 and 9.3 ng/mL, respectively. Patients with LNR values of ≥0.48 had a significantly worse disease-free survival (DFS) than those with LNR values of <0.48 (P = 0.015), and patients with pre-ablation sTg level values of ≥9.3 ng/mL had significantly worse DFS than those with pre-ablation sTg level values <9.3 ng/mL (P < 0.001). Relative to patients with LNR values of <0.48, those with LNR values of ≥0.48 had higher median pre-ablation sTg level values (0.55 vs. 4.20; P < 0.001). The correlation covariant between the LNR value and the pre-ablation sTg level value was r = 0.454 (P < 0.001). Multivariate analysis showed that a LNR value of ≥0.48 (P = 0.386) was not an independent risk factor for recurrence. To the contrary, a pre-ablation sTg level value of ≥9.3 ng/mL (P < 0.001) was an independent risk factor for recurrence.

Conclusion A high pre-ablation sTg level is a better predictor of recurrence in pathological N1a PTC than a high LNR value. Careful follow-up of patients with this risk factor is recommended.