SIZE OF THE LARGEST METASTATIC FOCUS TO THE LYMPH NODE IS ASSOCIATED WITH INCOMPLETE RESPONSE OF PN1 PAPILLARY THYROID CARCINOMA.

Abstract

Objective: To evaluate the influence of the size of the metastatic focus in lymph node ( LN ) on therapeutic response among papillary thyroid cancer (PTC) and cervical pathologically proven LN metastases (pN1). Methods: Patients with pN1 PTC who underwent total or near-total thyroidectomy, LN dissection and postoperative radioactive iodine therapy in a university hospital between 2014 and 2016 were retrospectively reviewed. Furthermore, 554 patients were assigned to three groups according to the size of the metastatic focus in the LN (⩽0.2 cm, 0.2-1.0 cm, ⩾1.0 cm). The structural incomplete response (SIR) was defined as the structural or functional evidence of disease with any Tg level and/or TgAb. Results: Among the 554 patients, the proportion of patients with SIR was identified in 2.5% (4/161) of group 1, 13.9% (37/267) of group 2 and 46.8% (59/126) of group 3 (χ2= 100.073, p < 0.001). The optimal cutoff value of the size of the largest metastatic focus to the LN was 0.536 cm to predict SIR with a corresponding sensitivity of 0.820, a specificity of 0.716, and an area under the curve (AUC) of 0.821 (95% CI 0.777-0.864; p < 0.001). Size of the largest metastatic focus to the LN was confirmed to be an independent predictive factor for SIR (OR = 9.650, 95% CI 4.925-18.909; p < 0.001). Conclusion: In patients with pN1 PTC, there is an association between the size of the largest metastatic focus to the LN and incomplete response.